A total of 300 male adult Wistar rats (180-220 g) were used. Animals were divided into four groups: control, vinyl chloride (VC) 10-, 100-, and 3000-ppm exposed groups. Seventy-five rats were used for each group. Inhalation exposure to VC was conducted 6 hr per day and 6 days per week. In the third, sixth, and twelfth month following exposure 8-30 rats of each group were killed. The others were under observation and sacrificed after 18 months. After exposure to VC, the organ and body weight ratio, such as the kidney, liver, spleen, and heart were increased, but those of the testis were decreased in the experimental groups in the sixth month. The differences between experimental groups and the control group were statistically significant (P less than 0.05 or P less than 0.01). The weights of testis were decreased and damage of testicular seminiferous tubules were found in rats by histopathological examination. Incidence of damage of testicular seminiferous tubules in the control, 10-, 100-, and 3000-ppm groups were 18.9, 29.7, 36.5, and 56.0%, respectively. There was an obvious dose-response relation between the concentration of VC and the incidence of testis damage, with a correlation coefficient of 0.993 (P less than 0.01). Statistically, the incidence of damage of testicular seminiferous tubules in rats in the 3000-ppm group and in 100-ppm group were significantly higher than that of the control group, respectively (P less than 0.001) and P less than 0.05).