This European Organization for Research and Treatment of Cancer (EORTC) trial 30853 is the fifth EORTC--Genitourinary Group randomized phase III trial of endocrine treatment for patients with newly diagnosed metastatic prostate cancer. Special attention was given to the assessment of response and/or progression. Each of the following factors was assessed separately as nonspecific and subjective criteria of response or progression: performance status, pain, alkaline and acid phosphatase, hemoglobin, urinary symptoms, and prostate-specific antigen (PSA). Objective progression was based on measurable disease. The observed sequence of progression was: (1) protein-specific antigen; (2) bone; (3) pain; and (4) performance status. Protein-specific antigen, an optional parameter, was the first sign of progression in more than 50% of patients whose disease had progressed.