In the present study, an attempt has been made to assess whether the effect of benzene extract of Ocimum sanctum leaves on the spermatogenic pattern and ultrastructure changes in testis of albino rats. Wistar strain male albino rats were orally administered 250 mg/kg body weight of O.sanctum leaves followed by maintaining suitable controls for 48 days. Results indicate that spermatogenesis was arrested either at the primary spermatocytes or the spermatogonial stages. Damaged seminiferous tubules and abundance of vacuoles of varying size were observed. Total count and diameter of spermatogonia, spermatocytes, spermatids and Leydig cells were reduced. Ultrastructural analysis revealed that intercellular spaces primarily, though not exclusively in the Sertoli cell cytoplasm, degeneration started within the nucleus of spermatocytes and from acrosomal granule or Golgi complex of round spermatids. Bridges between Sertoli cells–spermatocytes or spermatids were disturbed and most of mitochondria of cytoplasm were hypertrophied. Within the cytoplasm degenerating spermatids were with less electron dense matrix and commencement of vacuolization. The results suggest that the effect of benzene extract of O.sanctum leaves on the rat testis may be due to curtailing of androgen supply within the testis through its antispermatogenic and antiandrogenic property.