The authors have studied the prognostic interest of evaluating the prostatic acid phosphatase level before any treatment in 84 cases of stage B and C prostatic cancer. An abnormal PAP level did not significantly modify the 5-year life expectancy of patients, but was significantly correlated with a shorter period of disease-free survival. An abnormal PAP level increased the risk of recurrence; the higher the PAP level, the shorter the disease-free interval was. The disease stage (i.e., B or C) did not modify the 5-year survival period or the length of the remission. The prognosis is worse for a stage B prostatic cancer with a pathological PAP level than for a stage C cancer with a normal PAP level. A pathological PAP level seems to indicate the presence of occult metastases and should incite the clinician to actively investigate the matter.