Prostatic carcinoma often shows different behavior in the primary site than in the metastases after endocrine treatment. The pattern of disease progression was evaluated in prostate cancer patients. Two hundred and sixty consecutive patients were observed following the initiation of endocrine treatment (11 patients with stage T1 disease, 42 with stage T2 70 with stage T3, 11 with N + M0 and 126 with stage M1 disease). Of the 117 patients whose disease progressed, 100 could be evaluated in terms of the pattern of disease progression. Twenty-two (64.7%) of the 34 patients with stage T1-3N0M0 showed a pattern of local progression. On the other hand, 56 (84.8%) of the 66 patients with stage N + or M1 experienced a pattern of distant progression. Patients with only distant progression numbered 36 cases and patients with local progression and distant progression numbered 20 cases. Most of the distant progressions appeared in bone site. Local progression was observed in only 30 (45.5%) patients with stage N + or M1 disease. In patients with localized disease (T1-3N0M0), both the interval to disease progression and the time to cancer death from the start of disease progression were significantly longer than those of patients with stage N + or M1. However, once bone metastasis occurred, the disease tended to progress rapidly. There was no significant difference between the interval to cancer death after the appearance of bone metastasis in patients with initially localized stages (T1-3N0M0) and the time to cancer death after disease progression in patients with metastatic disease (N + or M1). The study shows a heterogenous behavior of the prostatic tumor after endocrine treatment. This suggests that metastases and primary tumor have different clonal compositions. The study also supports the idea that there is a preferential environment for the growth of prostatic carcinoma cells in bone sites.