Tabasco sauce and mustard taken with the evening meal markedly disturbed sleep of six, young, healthy male subjects; reducing slow wave and stage 2 sleep, increasing total time awake and tending to increase sleep onset latency. Whilst post meal effects on temperature and oxygen consumption were not significantly different from control meals the spicy food condition elevated body temperature during the first sleep cycle. The possibility that the spice principle capsaicin affects sleep via changes in body temperature is discussed.