BACKGROUND We developed non-invasive, cell-based screening assays to rapidly and biologically assess factors that modulate prostate cancer growth and affect androgen receptor (AR) activity. METHODS LNCaP cells, which stably express enhanced green fluorescent protein (EGFP) either constitutively or upon AR activation, were treated with a variety of agents, and then monitored by fluorescence and MTS assays for dose-dependent changes in cell number and AR activity. RESULTS The assays were validated for rapid, fluorescence-based, quantitative measurement for the presence of growth and AR modulators. Using these assays, we found that osteoblast conditioned media (CM) enhanced prostate cancer cell growth, but not AR activity. After priming with androgen (<1 nM R1881), forskolin or the pesticide dichlorvos enhanced AR activation, whereas interleukin-6 (IL-6) inhibited it. CONCLUSION These non-destructive, cell-based assays enable rapid systematic monitoring of the effects of drugs or complex mixtures on prostate cancer cell growth and/or AR activity.