We have analyzed the effects of the 5alpha-reductase inhibitor, finasteride (MK906), on the mRNA expression of the epidermal growth factor receptor and c-erbB-2 genes, in benign prostatic hyperplasia explant cultures treated with testosterone and with testosterone plus finasteride. A decrease of the epithelial cell content and an androgen-independent basal cell re-epithelialization was observed during the first 10 days of culture, suggesting a role of basal cells as stem cells involved in androgen-independent epithelial regeneration. Using a semi-quantitative reverse transcription polymerase chain reaction technique, we observed a significant decrease in expression of the epidermal growth factor receptor in the cultures treated with finasteride whereas no effect of finasteride on c-erbB-2 transcription was detected, although the expression of both genes was increased by dihydrotestosterone.