The efficacy of treating carcinoma of the prostate with levodopa (L-dopa), a known inhibitor of prolactin secretion, has been tested in 11 Stage D patients who were refractory to conventional modalities. Relief of bone pain and recovery of mobility was excellent in 6, fair in 2, questionable in 1, and nonexistent in 2. Acid phosphatase, where initially found to be elevated, was reduced to normal limits.