Usually when a patient takes a nighttime hypnotic, he expects early onset of pharmacological activity. At bedtime most patients are not fasting. The effect of fed vs fasting conditions on the onset, rate, and extent of absorption of an orally administered hypnotic, tritiated capuride (capuride-4,5-3H), has been studied. Five subjects received the drug while fasting and after a heavy meal. The meal produced a significant prolongation of the time between tablet ingestion and appearance of the drug in the plasma. This produced a significant decrease in the rate constant for absorption. Absorption lag time and absorption halftime are approximately 6.5 times longer in the presence of food than in its absence. However, the extent of absorption was not changed. A potentially dangerous situation may arise due to delayed but complete absorption of hypnotic agents in nonfasting patients.