A 79-year-old man complained of pollakisuria and sense of retention. The prostate was stony hard and heterogeneously enhanced on computed tomographic (CT) scan. The serum levels of prostatic specific antigen, prostatic acid phosphatase and gamma-Seminoprotein were abnormally high. Prostatic biopsy showed mucinous adenocarcinoma which was stained by prostatic specific antigen. Bone scintigraphy revealed multiple metastases. Hormonal therapy was performed. Each prostatic tumor marker decreased to the normal range within 2 months. After 3 months, the prostate was almost normalized on digital examination and CT scan. There were no new metastases, prostatic biopsy revealed that most cancer cells had degenerated to nonviable cells and bone metastases had decreased.