PURPOSE: Solvent containing 2-bromopropane has been widely used as a detergent in the electronic industries. The long-term toxic effects of this chemical on spermatogenesis were investigated. MATERIALS AND METHODS: All eight employees (mean age 33 years) who were exposed to the solvent underwent semen analysis, hormonal tests, and testicular biopsies 2 to 3 months after cessation of the exposure. The patients' semen quality had been followed at regular intervals for 1 year as long as the results remained abnormal. We monitored the long-term outcome of 3 patients whose semen remained abnormal during 1 year of follow-up. RESULTS: All patients had decreased sperm counts, with azoospermia being found in one patient. Six patients showed abnormal histologic findings such as atrophy of the seminiferous tubules, thickening of the basement membrane, and hyperplasia of Leydig cells. Of 8 patients, 5 (mean age 37.3 years) showed complete recovery of semen quality during the year after exposure ceased. These patients initially had sperm numbers more than 75 104/mL and a normal serum concentration of FSH. Of 3 patients with abnormal serum FSH and sperm numbers below 3,000/mL, 2 recovered normal sperm numbers at 18th and 24th months after cessation of exposure. Their ages and initial serum FSH concentration were 29 and 26 years and 19.6 and 74.7 mIU/mL, respectively. One patient (37 years old) with relatively normal testicular histology and a serum FSH concentration of 23.7 mIU/mL still had abnormal findings at the last semen analysis, performed 6 years after cessation of exposure. CONCLUSIONS: Solvent containing 2-bromopropane can impair spermatogenesis. This process may be reversed by avoidance of the exposure to this chemical substance. However, an abnormally elevated serum FSH concentration after exposure is an ominous sign for recovery of semen quality.