Out of 1,000 children (aged 3-12 years) screened in a paediatric outpatient department over a 3 1/2-year period, 112 were found to have attention deficit disorder with hyperactivity (ADDH). The prevalence of ADDH increased with age, from 5.2% in those aged 3-4 years, up to 29.2% in those aged 11-12 years. There were four times as many boys as girls with ADDH. ADDH was most common in first born children and those from a lower social class. Children with ADDH had a higher rate of complications during pregnancy and delivery relative to a comparison group. Delayed development, temper-tantrums, enuresis, tics, broken homes, persistent parental discord and psychiatric illness in parents were all more common in children with ADDH than in the comparison group.