Dibromochloropropane (DBCP) is an effective nematocide which was shown to suppress spermatogenesis and cause infertility in men and rats exposed to the compound. These damages were described only after 6-8 weeks post injection. The present study was set to detect the early development of the testicular damages. Rats were injected s.c. with DBCP 50 mg/kg. Control animals were injected with the vehicle alone (DMSO). Groups of animals were sacrificed 24 h, 1, 2, 3 and 4 weeks post injection. Body weight of DBCP treated animals was reduced from the second week post injection. Organs' weights of the DBCP treated rats, corrected for differences in body weights, were similar to those of controls. Four weeks post injection testes and accessory gland weights were significantly reduced as compared with controls. Percentage of damaged tubules in the DBCP treated animals were elevated from 16.6 +/- 3.5 at the first day to 70.2 +/- 6.4 at the 4th weeks. Concomitantly with the advance of tubular damage was a reduction in epididymal sperm count in the DBCP treated rats. One week post injection histological changes were evident. These included multinucleated giant cells and tubules blocked with sperm granuloma. It seems that alterations of spermatogenesis appear earlyer and are already noticeable one week post injection.