We have evaluated, by means of stereological analysis, the dimensions of the lymph node functional areas (cortical, medullary, paracortical, histiocytosis of the sinuses, germinal centers) in regional lymph nodes of women with cervical cancer (15 women) and endometrial carcinoma (6 women) in Ist and IInd stage, treated 8 days before surgery with a dose of 1-1.5 mg/kg of body weight of thymostimulin directly into the uterine cervix. 4 women with cervical and endometrial cancer (stages I and II) and treated with the same doses of physiological saline solution were used as controls. The quantitative results show that in the lymph nodes of women treated with thymostimulin there is a statistically significant marked increase (P less than 0.001), of the paracortical areas.