After prolonged toluene-inhalation (for 20 days) at the common abuse density (1500 ppm for 4 h per day), the effect of toluene on spermatogenesis in rats was investigated. Body weight was significantly decreased in the toluene group (P < 0.05). However, the weights of the testis and epididymis were maintained. To confirm whether the toluene-inhalation influences testis and epididymis as a stress factor; anti-70kD heat-shock protein (HSP70) and c-fos gene product (c-Fos) were observed. To observe the change of the cell division and the proliferation in spermatogenesis, proliferating cell nuclear antigen (PCNA) were stained immunohistochemically, and apoptosis was also detected. There was no positive immunoreactivity for HSP70 or c-Fos. There was no significant difference in the PCNA-expression in both groups. It was considered that toluene-inhalation did not have a clear influence in the division of spermatogonium and spermatocytes. On in situ apoptosis detection, slightly enhanced signals were observed in the toluene-inhalation groups. This might have some influence on meiosis from spermatocyte to spermatid. However, in toluene-inhalation rats exposed to a common abuse density, it was considered that spermatogenesis was well maintained and not apparently damaged.