Résumé : The possibilities of computerized axial tomography in the study of pelvic and lower abdominal tumors were explored, using as a first study a series of 10 observations. The general radiologic aspect of the region by CAT is described, as well as that of the principal organs and their component parts. From the beginning, this method has proven to be of great value in the diagnosis and delimitation of peritoneal and pelvic tumors. Furthermore, the demonstration of muscular structures in the region is without equal when compared to the results obtained with other techniques.