Urogenital sinus mesenchyme (UGM) from normal, androgen receptor-positive mice appears to instructively induce prostatic morphology in urinary tract epithelium from both normal and androgen-insensitive (Tfm) mice. This indicates that epithelial androgen receptors are not necessary for prostatic development. However, the secretory function of these tissue recombinants has never been assessed. In this study antisera to androgen-dependent dorsolateral prostate (DLP) secretion were used in immunocytochemistry, Western blotting, and immunoprecipitation techniques to detect the presence of these prostatic proteins in tissue recombinants made with either normal or Tfm epithelium. In a majority of cases, UGM plus normal bladder or urethral epithelium developed into prostatic tissue that produced androgen-dependent DLP proteins. Hence UGM appeared to be capable of instructively inducing a functional prostatic phenotype in these normal heterotypic epithelia. With rare exceptions, tissue recombinants of UGM plus Tfm bladder or urethral epithelium did not produce full prostatic cytodifferentiation or mouse DLP proteins, indicating that epithelial androgen receptors are important for the final stages of morphogenesis and in the initiation of secretory function in the prostate.