Prostates from patients with prostatic hyperplasia were maintained in organ culture for periods up to 8 days. Explants were disaggregated and studied after 2, 4 and 8 days of culture and before culture. Although the data varied from patient to patient, short periods of culture (2-4 days) resulted in increased numbers of cells with histochemically demonstrable acid phosphatase; however, by 8 days of culture, cells with histochemically demonstrable acid phosphatase decreased in number. The ratio of acid phosphatase to .beta.-glucuronidase expressed per cell or per mg of protein decreased with time in culture.