The aim was to detect abnormalities in the circadian temperature rhythms of narcoleptic patients, as evidence of abnormal circadian pacemaker function. Six narcoleptic patients and nine normal controls lived in a time-isolation laboratory for 18-22 days. Rectal temperature was measured every minute and modeled by mean waveforms and cosine functions, which have complementary advantages. In this study, the two types of models gave similar results: The levels, periods, amplitudes, and phases of the circadian temperature rhythms of patients and controls did not significantly differ--evidence against an abnormality of circadian pacemaker function in narcolepsy. The increases of temperature that normally follow main sleep periods were smaller in narcoleptic subjects, and narcoleptic naps, which were involuntary, were heralded and accompanied by small decreases of mean temperature.