This report describes the separation of cells exhibiting histochemically demonstrable acid phosphatase from suspensions of cells obtained from human prostatic carcinomas by velocity sedimentation. In the unseparated suspensions of cells, 40.5 ± 7.7% of nucleated cells contained histochemically evident acid phosphatase. After cells were separated by velocity sedimentation, 86.4 ± 9.4% of the nucleated cells in the purest fractions exhibited histochemically demonstrable acid phosphatase activity. More than 95% of these cells excluded trypan blue. This appears to be the first report of a method for the separation of viable epithelial cells from human prostatic carcinomas.