One hundred and fifty mentally handicapped people (100 from hospital and 50 from the community) with epilepsy were studied along with an individually matched control group of 150 (100 from hospital and 50 from the community) non-epileptic mentally handicapped people. Behaviour was studied using the Profile of Abilities and Adjustment Schedule. Of the total population, 55.3% showed some type of severe behaviour problem. Although the epileptics showed slightly more severe behaviour problems than the non-epileptic group, there was no statistically significant difference between the two groups. Some differences emerged between the groups when subgroups of epileptics were studied.