It is important to control abnormal behaviour and hyperactivity, and improve cognition in mentally retarded children (MRC), which would help in their education, training and subsequent rehabilitation. Recently it has become known that amongst other side-effects, protracted use of anti-convulsant medication induces cognitive and behavioural dysfunction, which is a major problem in mentally retarded epileptics. In a placebo-controlled study, we confirmed the efficacy of a herbal preparation, BR-16A (Mentat) in controlling such behavioural and cognitive deficits in 40 mentally retarded children. The efficacy of this remedy was further evaluated in 19 MRCs with epilepsy. Twelve patients had generalised seizure, 4 with partial and 3 with mixed seizure pattern was continued. Inspite of the usual antiepileptic treatment, the frequency of seizures ranged from 1 to 7 attacks in periods from 1 week to 1 year. With active drug Br-16A, it was possible to note a reduction in seizure frequency. Patients with higher frequency responded better. There was no further increase in the dosage of antiepileptic drugs. There was significant control of other abnormal behaviour as shown by reduction in rating score on the Children's Behavioural Inventory test. BR-16A was effective in controlling abnormal behaviour, especially hyperactivity and incongruous behaviour in mentally retarded children with and without epilepsy.