The current study was undertaken, using cultures of prostatic epithelial and stromal cells, to determine the functional interactions between androgens, basic fibroblast growth factor (FGF2) and transforming growth factor-beta 1 (TGF beta 1) and their importance in maintaining stromal homeostasis. Treatment of stromal cells with TGF beta 1 significantly increased intracellular FGF2 and FGF2 sequestered to the extracellular matrix. FGF2 was also detected in stromal conditioned medium (SCM), but at levels 70-fold less than found in cell lysates. TGF beta 1 (0.1 ng/ml) treatment caused an initial increase of 86% in secreted FGF2 levels, but high concentrations of TGF beta 1 (5 ng/ml) decreased FGF2 levels by 38%, relative to the untreated control. Further studies showed that epithelial conditioned medium (ECM), androgen-treated, stromal conditioned medium (ASCM), but not SCM were mitogenic for stromal cells. Both ECM and ASCM caused a threefold increase in DNA synthesis. FGF2 may be the mediator of these interactions, since the mitogenic effect of both ECM and ASCM was significantly reduced by the addition of anti-FGF2 neutralising antibody. We hypothesise that the lack of response of stromal cells to SCM is due to TGF beta 1 blocking the mitogenic effect of FGF2. Thus down-regulation of TGF beta 1 synthesis, by androgens, results in stromal proliferation by ASCM.