Forty-seven patients who had been treated for brain tumours during childhood were assessed on standardized measures of intellectual ability. Five patients could not be satisfactorily assessed. For the remaining 42, the mean IQ was lower than expected (09.0), with 20 patients having scores in the 'below average' categories. There were no apparent effects in IQ between patients treated for different tumours, but patients treated before five years of age had significantly lower scores (mean equal 76.54) than patients treated from 6-10 years (mean 91.86) and 10-16 years (99-93). There was wide variability in educational achievement and type of employment among the group.