Histomorphometric study of hyperplastic human prostate explants coating grown "in vitro" to evaluate the response to a 5-alpha-reductase inhibitor (finasteride). Explants were grown for four weeks in three groups, one in growth medium alone (RPM1-1640), one supplemented with testosterone and one supplemented with testosterone plus finasteride. Explants underwent histological studies, quantifying the surface and thickness of the coating epithelium. Study of the values obtained from the different samples show significant differences (p < 0.001) for the coated surface and its thickness between groups supplemented with testosterone and testosterone + finasteride, and so it can be inferred that this compound (finasteride) would blockade basal cells proliferation and their migration on the explant surface.