diff --git a/moto/ec2/exceptions.py b/moto/ec2/exceptions.py
index 1bba89fd5..79ceb776f 100644
--- a/moto/ec2/exceptions.py
+++ b/moto/ec2/exceptions.py
@@ -318,3 +318,11 @@ class InvalidCIDRSubnetError(EC2ClientError):
             "InvalidParameterValue",
             "invalid CIDR subnet specification: {0}"
             .format(cidr))
+
+
+class RulesPerSecurityGroupLimitExceededError(EC2ClientError):
+    def __init__(self):
+        super(RulesPerSecurityGroupLimitExceededError, self).__init__(
+            "RulesPerSecurityGroupLimitExceeded",
+            'The maximum number of rules per security group '
+            'has been reached.')
diff --git a/moto/ec2/models.py b/moto/ec2/models.py
index a3e333dc7..5d220a0e2 100755
--- a/moto/ec2/models.py
+++ b/moto/ec2/models.py
@@ -58,6 +58,7 @@ from .exceptions import (
     InvalidVpnGatewayIdError,
     InvalidVpnConnectionIdError,
     InvalidCustomerGatewayIdError,
+    RulesPerSecurityGroupLimitExceededError,
 )
 from .utils import (
     EC2_RESOURCE_TO_PREFIX,
@@ -1264,6 +1265,16 @@ class SecurityGroup(TaggedEC2Resource):
     def add_egress_rule(self, rule):
         self.egress_rules.append(rule)
 
+    def get_number_of_ingress_rules(self):
+        return sum(
+            len(rule.ip_ranges) + len(rule.source_groups)
+            for rule in self.ingress_rules)
+
+    def get_number_of_egress_rules(self):
+        return sum(
+            len(rule.ip_ranges) + len(rule.source_groups)
+            for rule in self.egress_rules)
+
 
 class SecurityGroupBackend(object):
 
@@ -1360,6 +1371,10 @@ class SecurityGroupBackend(object):
                 if not is_valid_cidr(cidr):
                     raise InvalidCIDRSubnetError(cidr=cidr)
 
+        self._verify_group_will_respect_rule_count_limit(
+            group, group.get_number_of_ingress_rules(),
+            ip_ranges, source_group_names, source_group_ids)
+
         source_group_names = source_group_names if source_group_names else []
         source_group_ids = source_group_ids if source_group_ids else []
 
@@ -1425,6 +1440,10 @@ class SecurityGroupBackend(object):
                 if not is_valid_cidr(cidr):
                     raise InvalidCIDRSubnetError(cidr=cidr)
 
+        self._verify_group_will_respect_rule_count_limit(
+            group, group.get_number_of_egress_rules(),
+            ip_ranges, source_group_names, source_group_ids)
+
         source_group_names = source_group_names if source_group_names else []
         source_group_ids = source_group_ids if source_group_ids else []
 
@@ -1472,6 +1491,20 @@ class SecurityGroupBackend(object):
             return security_rule
         raise InvalidPermissionNotFoundError()
 
+    def _verify_group_will_respect_rule_count_limit(
+            self, group, current_rule_nb,
+            ip_ranges, source_group_names=None, source_group_ids=None):
+        max_nb_rules = 50 if group.vpc_id else 100
+        future_group_nb_rules = current_rule_nb
+        if ip_ranges:
+            future_group_nb_rules += len(ip_ranges)
+        if source_group_ids:
+            future_group_nb_rules += len(source_group_ids)
+        if source_group_names:
+            future_group_nb_rules += len(source_group_names)
+        if future_group_nb_rules > max_nb_rules:
+            raise RulesPerSecurityGroupLimitExceededError
+
 
 class SecurityGroupIngress(object):
 
diff --git a/tests/test_ec2/test_security_groups.py b/tests/test_ec2/test_security_groups.py
index 204380562..83dad6f0c 100644
--- a/tests/test_ec2/test_security_groups.py
+++ b/tests/test_ec2/test_security_groups.py
@@ -379,6 +379,136 @@ def test_authorize_all_protocols_with_no_port_specification():
     sg.rules[0].to_port.should.equal(None)
 
 
+@mock_ec2
+def test_sec_group_rule_limit():
+    ec2_conn = boto.connect_ec2()
+    sg = ec2_conn.create_security_group('test', 'test')
+    other_sg = ec2_conn.create_security_group('test_2', 'test_other')
+
+    # INGRESS
+    with assert_raises(EC2ResponseError) as cm:
+        ec2_conn.authorize_security_group(
+            group_id=sg.id, ip_protocol='-1',
+            cidr_ip=['{0}.0.0.0/0'.format(i) for i in range(110)])
+    cm.exception.error_code.should.equal('RulesPerSecurityGroupLimitExceeded')
+
+    sg.rules.should.be.empty
+    # authorize a rule targeting a different sec group (because this count too)
+    success = ec2_conn.authorize_security_group(
+        group_id=sg.id, ip_protocol='-1',
+        src_security_group_group_id=other_sg.id)
+    success.should.be.true
+    # fill the rules up the limit
+    success = ec2_conn.authorize_security_group(
+        group_id=sg.id, ip_protocol='-1',
+        cidr_ip=['{0}.0.0.0/0'.format(i) for i in range(99)])
+    success.should.be.true
+    # verify that we cannot authorize past the limit for a CIDR IP
+    with assert_raises(EC2ResponseError) as cm:
+        ec2_conn.authorize_security_group(
+            group_id=sg.id, ip_protocol='-1', cidr_ip=['100.0.0.0/0'])
+    cm.exception.error_code.should.equal('RulesPerSecurityGroupLimitExceeded')
+    # verify that we cannot authorize past the limit for a different sec group
+    with assert_raises(EC2ResponseError) as cm:
+        ec2_conn.authorize_security_group(
+            group_id=sg.id, ip_protocol='-1',
+            src_security_group_group_id=other_sg.id)
+    cm.exception.error_code.should.equal('RulesPerSecurityGroupLimitExceeded')
+
+    # EGRESS
+    # authorize a rule targeting a different sec group (because this count too)
+    ec2_conn.authorize_security_group_egress(
+        group_id=sg.id, ip_protocol='-1',
+        src_group_id=other_sg.id)
+    # fill the rules up the limit
+    # remember that by default, when created a sec group contains 1 egress rule
+    # so our other_sg rule + 98 CIDR IP rules + 1 by default == 100 the limit
+    for i in range(98):
+        ec2_conn.authorize_security_group_egress(
+            group_id=sg.id, ip_protocol='-1',
+            cidr_ip='{0}.0.0.0/0'.format(i))
+    # verify that we cannot authorize past the limit for a CIDR IP
+    with assert_raises(EC2ResponseError) as cm:
+        ec2_conn.authorize_security_group_egress(
+            group_id=sg.id, ip_protocol='-1',
+            cidr_ip='101.0.0.0/0')
+    cm.exception.error_code.should.equal('RulesPerSecurityGroupLimitExceeded')
+    # verify that we cannot authorize past the limit for a different sec group
+    with assert_raises(EC2ResponseError) as cm:
+        ec2_conn.authorize_security_group_egress(
+            group_id=sg.id, ip_protocol='-1',
+            src_group_id=other_sg.id)
+    cm.exception.error_code.should.equal('RulesPerSecurityGroupLimitExceeded')
+
+
+@mock_ec2
+def test_sec_group_rule_limit_vpc():
+    ec2_conn = boto.connect_ec2()
+    vpc_conn = boto.connect_vpc()
+
+    vpc = vpc_conn.create_vpc('10.0.0.0/8')
+
+    sg = ec2_conn.create_security_group('test', 'test', vpc_id=vpc.id)
+    other_sg = ec2_conn.create_security_group('test_2', 'test', vpc_id=vpc.id)
+
+    # INGRESS
+    with assert_raises(EC2ResponseError) as cm:
+        ec2_conn.authorize_security_group(
+            group_id=sg.id, ip_protocol='-1',
+            cidr_ip=['{0}.0.0.0/0'.format(i) for i in range(110)])
+    cm.exception.error_code.should.equal('RulesPerSecurityGroupLimitExceeded')
+
+    sg.rules.should.be.empty
+    # authorize a rule targeting a different sec group (because this count too)
+    success = ec2_conn.authorize_security_group(
+        group_id=sg.id, ip_protocol='-1',
+        src_security_group_group_id=other_sg.id)
+    success.should.be.true
+    # fill the rules up the limit
+    success = ec2_conn.authorize_security_group(
+        group_id=sg.id, ip_protocol='-1',
+        cidr_ip=['{0}.0.0.0/0'.format(i) for i in range(49)])
+    # verify that we cannot authorize past the limit for a CIDR IP
+    success.should.be.true
+    with assert_raises(EC2ResponseError) as cm:
+        ec2_conn.authorize_security_group(
+            group_id=sg.id, ip_protocol='-1', cidr_ip=['100.0.0.0/0'])
+    cm.exception.error_code.should.equal('RulesPerSecurityGroupLimitExceeded')
+    # verify that we cannot authorize past the limit for a different sec group
+    with assert_raises(EC2ResponseError) as cm:
+        ec2_conn.authorize_security_group(
+            group_id=sg.id, ip_protocol='-1',
+            src_security_group_group_id=other_sg.id)
+    cm.exception.error_code.should.equal('RulesPerSecurityGroupLimitExceeded')
+
+    # EGRESS
+    # authorize a rule targeting a different sec group (because this count too)
+    ec2_conn.authorize_security_group_egress(
+        group_id=sg.id, ip_protocol='-1',
+        src_group_id=other_sg.id)
+    # fill the rules up the limit
+    # remember that by default, when created a sec group contains 1 egress rule
+    # so our other_sg rule + 48 CIDR IP rules + 1 by default == 50 the limit
+    for i in range(48):
+        ec2_conn.authorize_security_group_egress(
+            group_id=sg.id, ip_protocol='-1',
+            cidr_ip='{0}.0.0.0/0'.format(i))
+    # verify that we cannot authorize past the limit for a CIDR IP
+    with assert_raises(EC2ResponseError) as cm:
+        ec2_conn.authorize_security_group_egress(
+            group_id=sg.id, ip_protocol='-1',
+            cidr_ip='50.0.0.0/0')
+    cm.exception.error_code.should.equal('RulesPerSecurityGroupLimitExceeded')
+    # verify that we cannot authorize past the limit for a different sec group
+    with assert_raises(EC2ResponseError) as cm:
+        ec2_conn.authorize_security_group_egress(
+            group_id=sg.id, ip_protocol='-1',
+            src_group_id=other_sg.id)
+    cm.exception.error_code.should.equal('RulesPerSecurityGroupLimitExceeded')
+
+
+
+
 '''
 Boto3
 '''