OBJECTIVE Microdissection testicular sperm extraction (TESE) is the ideal procedure for obtaining a high sperm retrieval rate. However, few studies of the postoperative endocrinologic course have been reported. We evaluated the endocrinologic course for 1 year after microdissection TESE and compared the results with the testicular histologic findings. METHODS A total of 69 patients with nonobstructive azoospermia who had undergone microdissection TESE were included. The overall sperm retrieval rate was 50.7%. The endocrinologic data were evaluated before and 3, 6, and 12 months after surgery. RESULTS The mean serum total testosterone level in patients with hypospermatogenesis decreased postoperatively and had recovered by 12 months (102%). The mean serum total testosterone level in patients with Klinefelter syndrome also decreased postoperatively but had recovered to only 50% of the baseline value at 12 months after microdissection TESE. At 12 months, the mean serum total testosterone level in patients with maturation arrest was 93.1% of the preoperative level and that in patients with Sertoli cell-only syndrome was 80.6% of the preoperative level. The preoperative serum luteinizing hormone and follicle-stimulating hormone in patients with Klinefelter syndrome was high and remained high after microdissection TESE. The mean serum luteinizing hormone and follicle-stimulating hormone levels in patients with hypospermatogenesis did not change, and those in patients with maturation arrest increased continuously after microdissection TESE. Finally, those in patients with Sertoli cell-only syndrome increased up to 6 months after surgery and decreased after that. CONCLUSIONS The results of our study indicate that long-term endocrinologic follow-up is necessary after microdissection TESE, particularly for patients with Klinefelter syndrome to detect hypogonadism.