One hundred and twenty unpremedicated patients, scheduled for minor gynaecological procedures, were randomly allocated to receive Althesin or methohexitone to supplement N2O and O2 anaesthesia. Patients were assessed as thin, medium or fat according to the degree of obesity as measured by skinfold calipers. The range of mean times for the patients to open their eyes was 3.1-4.0 minutes, to be orientated was 4.4-6.7 minutes and to perform a manipulative test was 27.7-32.1 minutes. No statistically significant differences were seen in these indices of recovery whether they received Althesin or methohexitone or whether they were thin, medium or fat. A paper and pencil test was also performed. Induction doses of the intravenous agent were calculated on a body weight basis and increments given only in response to movement. The mean total dose of Althesin was decreased from 1.33 mg total steroid/kg for thin patients to 1.06 mg total steroid/kg for fat patients (p less than 0.01). The mean total dose of methohexitone was decreased from 3.4 mg/kg for thin patients to 2.9 mg/kg for fat patients which was not significant.