By means of a morphometric analysis, the authors have evaluated the structure and dimensions of the lymph node functional areas (cortical, medullary, paracortical, histiocytosis of the sinuses, germinal centres) in regional nodes of women with carcinoma of the uterus in the 1st and 2nd stages. Twenty patients were treated 8 days before surgery with a dose of 1.5 mg kg-1 body weight of thymic hormone directly into the uterine portio. Ten patients, on the other hand, were injected with physiological saline solution. The quantitative and qualitative results show that in peritumoral lymph nodes of women treated with thymostimolin there is a marked increase, statistically significant (P less than 0.001), of the paracortical zone and of the number of germinal centres.