The methods described in this article seem to be useful for studies on the growth characteristics of malignant epithelial prostate cells which are still under the influence of healthy cells. Before establishing primary cultures, pieces of tissue were sectioned in such a way that they could be unfolded to obtain a large surface. These pieces were treated enzymatically and then incubated for at least 4-6 weeks. In this time, cells grew or migrated out of the tissue and spread over the surface of the culture flasks. The viable single cells harvested from these primary cultures were characterized flow cytometrically, fractionated by countercurrent centrifugal elutriation, or further incubated above agarose so that they formed three-dimensional spheroids. Cytometric determinations of cellular cytokeratin, vimentin, and DNA were performed before and after incubation. They suggested that the percentages of cytokeratin-positive (epithelial) cells, vimentin-positive cells (fibroblasts), and aneuploid cells remained at levels (in vitro) similar to those within the pieces of tissue used for the culturing experiments, respectively. Since our culture technique allows the propagation of human epithelial prostate cells in vitro as they would grow in vivo under the control of the surrounding tissue, the method should help to investigate which particular treatment of the cells influences the growth of the malignant cells, while they are still surrounded by other cells of the same prostatic organ.