Infantile spasms (IS) is an age-specific epilepsy which responds to anticonvulsant therapy but has a generally poor prognosis for normal psychomotor development. The subgroup of infants with a cryptogenic aetiology or whose therapy is initiated promptly is thought to have a more favourable prognosis. We retrospectively reviewed 28 infants with IS treated between 1990 and 1996 with adrenocorticotropic hormone (ACTH), valproic acid (VPA), or both, in order to correlate therapeutic response with long-term outcome. Mean age at onset of treatment was 6.4 months, with 57% of patients started within 1 month of IS appearance. IS was considered cryptogenic in 39%. The majority of infants responded to ACTH or VPA with a reduction in spasms of 75% or more. Total remission of seizures occurred in 52%. Death occurred in eight patients; mean duration of follow-up for survivors was 55 months. All subgroups based on age, aetiology, or treatment had poor outcomes, commonly with residual epilepsy, cerebral palsy or mental retardation. Conventional treatment for IS, even when initially successful in reducing spasms, is inadequate when viewed from a long-term developmental perspective, suggesting the need for novel innovative approaches for treating IS.