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In three independent studies, free cortisol levels after morning awakening were repeatedly measured in children, adults and elderly subjects (total n= 152). Cortisol was assessed by sampling saliva at 10 or 15 minute intervals for 30–60 minutes, beginning at the time of awakening for two days (Study 1 and 2) or one (Study 3) day, respectively. In all three studies, free cortisol levels increased by 50–75% within the first 30 minutes after awakening in both sexes on all days. Premenopausal women consistently showed a stronger increase with a delayed peak after awakening compared to men on all days. In Study 2, there was a tendency for lower early morning free cortisol levels for women taking oral contraceptives (p=.10). Stability of the area under the curve (AUC) of the early morning free cortisol levels over the three (Study 1 and 2) or two (Study 3) days ranged between r=.39 and r=.67 (p<.001). Neither age …