The activity of lipoprotein lipase (LPL) was measured in adipose tissue (AT-LPL) and postheparin plasma (PH-LPL) of 13 obese patients (aged 11 to 31 years) who had surgery for craniopharyngioma 1 to 13 years earlier. AT-LPL activity (mean +/- SEM) was higher in them than in subjects matched with respect to age, sex, and relative body weight (4.6 +/- 1.1 v 2.1 +/- 0.4 mumol free fatty acids (FFA).h-1.g-1, P less than .05). The activity was also higher when expressed per fat cell.