The subacute toxopathological effects of monocrotophos (Nuvacron) organophosphate insecticides was studied on male albino rats. Sixty male albino rats were devided into three equal groups. The first and the second groups were received 1/10 and 1/20 LD50 of Nuvacron®, daily for four weeks. The third group was kept as control. After two weeks, 5 animals from each group were sacrificed weekly and ten animals at the end of the treatment.. Tissue specimens were taken for histopathology, while serum samples were taken for hormonal assay only at the end of the treatment. Testosterone levels showed a highly significant increase in both the first and second groups in comparison to control group. The average levels of testosteron were 6049.833.1, 3394.6=25.6 and 1080.6–18.1 (pg/ml) in the first, second and control group, respectively. Estrogen levels were increased significantly in the first group. The average levels of estrogen were 17.9+0.02, 10.78+0.73 and 11.05+0.06 (pq/ml) in the three groups, respectively. Pathological examination of the testes revealed congestion of the blood vessels, intertubular oedema, fibroblastic proliferation followed by leydig cell hyperplasia, and hypertrophy. Degeneration of spermatogenic cells, atrophy of semineferous tubules and degeneration of vessel walls were noticed at the end of the experiment specially in the first group. The epididymis of the treated groups were empty from sperms and showed degeneration of their epithelium. The liver showed, degeneration and necrosis of the hepatic parenchyma. Our results concluded that, the effect of Nuvacron® on the testis was both directly on the spermatogenic cells and testicular blood vessel and indirectly through its effect on the intertubular tissue as well as on the liver