['We tested the hypothesis that a single exogenous androgen injection in men with low prostate specific antigen would provoke a differential prostate specific antigen response that would correlate with the presence and volume of cancer at biopsy.', 'Following institutional review board approval 40 men with prostate specific antigen between 2.5 and 4.0 ng/ml were given 1 intramuscular injection of 400 mg testosterone cypionate at the start of the study. Prostate specific antigen and early morning serum testosterone were measured at baseline, 48 hours, and weeks 1, 2 and 4. All men underwent 12-core transrectal ultrasound guided biopsy at week 4.', 'Of the 40 men 18 (45%) were diagnosed with prostate cancer. The mean change in prostate specific antigen from baseline to 4 weeks was 3.1 to 3.4 ng/ml (9.7%) in men found to have benign findings on biopsy compared to a mean increase of 2.9 to 3.8 ng/ml (29%) in those with prostate cancer (p = 0.006). The change in prostate specific antigen following androgen stimulation was significantly associated with the percent of tissue involved with cancer and it was an independent predictor of cancer diagnosis on univariate and multivariate analysis.'] Is change in prostate specific antigen following androgen stimulation an independent predictor of prostate cancer diagnosis?