The authors investigated neuroendocrine findings of H PA and HPT axes by DCT, DST, and T RH stimulation tests in patients with seasonal depressive disorder(SDD). Subjects were consisted of 11 inpatients(3 males, 8 females) with SDD and 10 control inpatients( l0 females) with non-seasonal depressive disorder(NSDD) at the Department of Psychiatry, Yonsei University Wonju Medical College from Sep. 1，1991 to Dec. 31, 1992. The results were as the following : 1) For DCT in SDD patients, 8 patients(72.6 95) showed abnormal cortisol secretion, two(l8.2 %) with distorted diumality and six(54.5%) with over-secretion pattern, which did not show significant difference from the control patients. 2) For DST, non-suppression rate was similiar in both group(36.4% for SDD vs 40.0% for NSDD ). 3) Blunted T RH stimulation test was noted in 5 among 11 SDD patients(45.5%) compared to 1 among 10 control patients(10.0%). 4) With DST and TRH stimulation test result, the diagnostic senstivity for patients with SDD(63.7%) was higher than that for NSDD patients(50.0%). 5) In patients with SDD, symptoms of decreased libido, increased duration of sleep and daytime drowsiness items by Boyce and Parker were more prevalent(P<0.05), and symptoms of early morning awakening, decreased duration of sleep were less prevalent(P<0.05).