Transrectal ultrasonotomography was performed in 44 patients with prostatic cancer before, during, and after estramustine phosphate (Estracyt) administration. In 75.7% of 37 previously untreated patients, the deformity of the horizontal section of the prostate with prostatic cancer was corrected considerably, while in 89.2%, prostatic weight was remarkably reduced. In 57.1% of seven previously treated patients, appreciable changes were also observed in the shape and weight of the prostate. We concluded that estramustine phosphate was effective not only for untreated prostatic cancer, but also, at least in some degree, for relapsed cases.