This thesis examines the following theory in several parts: across a wide range of experimental situations, changes in core body temperature (Tc) have been consistantly associated with inverse changes in sleep propensity. Previous research has focussed on the possible role that a declining Tc and distal vasodilation may play in normal nocturnal sleep onset. This research has lead to the suggestion that these changes in thermoregulation may mediate, or be functionally involved in, the regulation of sleep propensity in sedative-hypnotic agents.