Biochemical and physiological alterations have been observed in the genital tract of female cyclic rats treated with aqueous extract of M. oleifera Lam. Its administration caused a significant increase in the glycogen contents, protein concentration, activity of acid and alkaline phosphatase and the level of total cholesterol in all the organs at initial days of treatment. However, at longer days of treatment the values revealed a significant depletion. Initially its administration stimulated the uterine structures, caused metaplastic changes in the cervical epithelium and provoked considerable cornification in the vaginal epithelium. At later durations significant inhibition in the histoarchitecture was observed. Biochemical observations supplemented with the histological findings have been correlated with the anti-implantation action of the aqueous extract in the light of its hormonal properties.