Between 1989 and 1994, 18 children with cryptogenic infantile spasms – defined by normal development before onset of spasms, symmetrical hypsarrhythmia or multifocal spikes, and typical spasms on presentation, and no abnormal findings on aetiological studies including neuroradiology – were diagnosed and treated. To assess the risk of cognitive impairment later in life, 15 of these 18 children whose spasms completely resolved within the first year of life were studied. Age at onset of spasms varied between 4.4 and 9.8 months (mean 6.5 months). Children were effectively treated with adrenocorticotrophic hormone (10 children), pyridoxine (three), vigabatrin (one), or sodium valproate (one). Spasms lasted between 11 and 138 days (mean 50 days) and stopped between the age of 6.3 and 10.2 months (mean 8.1 months). EEGs normalized between the age of 7.1 and 13.2 months (mean 9.4 months). Early development was assessed on presentation and within a few months after spasms had stopped. A detailed neuropsychological assessment was performed between the age of 4.0 and 5.9 years. Twelve children had normal intelligence; specific cognitive deficits were found in five. Three children had mild learning disability. Abnormal developmental status at age 8 to 15 months after complete resolution of spasms and EEG abnormalities was associated with cognitive deficits at age 4 to 6 years.