[en] Objective: To study the rhythmic fluctuation of plasma cortisol levels in patients with EH and CHD. Methods: Plasma cortisol levels were determined with RIA at 8Am, 4Pm and midnight in 61 patients with EH, 46 patients with CHD and 36 controls. Results: The normal rhythmic fluctuation pattern of plasma cortisol levels was retained in the EH and CHD patients. However, the levels were all significantly higher in the patients than those in the controls, especially in the midnight specimens. Conclusion: Marked elevated plasma cortisol levels were observed in patients with EH and CHD, with the normal rhythmic fluctuation pattern retained. (authors)