Abstract: In this study the effect of aqueous extract of RG on spermatogenesis of rat has been investigated. Animals were allocated into three groups as: (1) control which did not receive anything, (2) vehicle which received only normal saline (the same volume as 3rd group according to the weight) and (3) experiment which received ruta extract (300 mg kg-1 intraperitoneally once a day for 50 days). A day after last injection the animals were deeply anesthetized and dissected. The right testes were extruded and fixed for histological studies. For statistical analysis ANOVA and Tukey as a post hoc. test were used. There was a significant decrease in the number of spermatogonia (p<0.01), primary spermatocyte (p<0.05), spermatid (p<0.05) and lydig cells (p<0.01) in experimental group as compared to control and vehicle. Also there were a significant increase in thickness of tunica albugina (p<0.01) and decrease in seminiferous tubule diameter (p<0.05) in experimental group compared to control and vehicle. So, it is concluded that the aqueous extract of Ruta graveolens diminishes the reproductive system activity and might be a useful substance for birth control process.