Plasma levels of diazepam and N-desmethyldiazepam were investigated in 19 children by a gas chromatographic method permitting the use of capillary sample. Intravenous administration was studied in 3 children and the plasma level curves showed a rapid decline during the first hour. Absorption and elimination after rectal administration of a solution in 16 children were similar to those after intramuscular administration. Diazepam given by suppository to 5 children gave much lower plasma levels and delayed time to peak levels. Recurrence of seizures in 2 children indicated that the anticonvulsants plasma level was of the order of 150 to 200 mug/liter. No significant side effects were observed. Thus rectal administration of a solution of diazepam is a practical method to arrest convulsions in children.