We studied 454 patients with prostatic adenocarcinoma who were assigned a preliminary clinical stage on the basis of serum acid phosphatase, routine bone survey and physical examination. Subsequently, they were assigned a final clinical stage after radioisotopic bone scanning, lymphangiography and staging pelvic lymph node dissection. Only 53, 54, 57 and 26 per cent, respectively, of patients initially assigned the preliminary clinical stage of IB, II, III or IVA remained at that stage after the additional studies.