Purpose: In vitro fertilization with intracytoplasmic sperm injection has resulted in a dramatic increase in the need for diagnostic and therapeutic testis biopsies. We developed a microsurgical testis biopsy technique which allows identification of testicular vessels and individual seminiferous tubules. We compare the results of this technique to our prior series of nonmicroscopic biopsies. Materials and Methods: A retrospective study of 226 consecutive patients who had undergone open testes biopsy with or without an operating microscope was performed. Between 1988 and 1994 standard open testis biopsy was performed without a microscope in 119 patients and a single sample of testicular tissue was taken. After 1994 microsurgical biopsy was performed under 6 to 25× magnification in 107 patients, nearly half of whom had multiple biopsies of each testis. The complication rates of the 2 procedures were compared. Results: Scrotal hematoma required surgical drainage in 3 of the 119 standard testis biopsy cases and testis atrophy was noted in 1, for a total complication rate of 3.4%. There were no episodes of clinically detectable testicular atrophy or scrotal hematoma requiring surgical drainage in the 107 microsurgical biopsy cases (p <0.05). In 2 men the microscope allowed identification of larger tubules that contained sperm. Conclusions: Use of the operating microscope for testicular biopsy allows identification and avoidance of testicular vessels, minimizing complications. It also may allow selection of seminiferous tubules more likely to contain sperm.