The effect of androgen depletion/repletion on the cell types of the rat ventral prostate has been studied using light microscope autoradiography and morphometric analysis. All prostatic cells were assigned to one of the following groups: epithelial, endothelial, stromal (periacinar), or stromal (interacinar). With the exception of the latter group, the numbers of all other cell types were significantly reduced by androgen depletion (castration), and increased by repletion thereafter. During the repletion period, the labeling index of all cell types rose in parallel and peaked 72 hours postinitiation of androgen replacement. The size of the proliferating pool just prior to the peak day was determined. Forty‐five percent of the total prostatic cell population was found to be labeled. The epithelial cell group contained the greatest proportion of labeled cells, but significant percentages occurred in the other types. These results precisely define the temporal effects of androgen replacement on prostatic cell population dynamics in the castrate rat.