OBJECTIVE To investigate whether there are different stromal compositions in the prostate tissue of patients with benign prostatic hyperplasia (BPH) and evaluate their significance in the course of the disease. METHODS Forty-three surgical or bioptic prostatic specimens of BPH and 5 autoptic normal prostatic specimens were stained by the Masson method to display the elements of the muscle fiber and collagen. The relationship of the changes in the prostatic stromal composition was analyzed with the degree of bladder outlet obstruction (BOO) , IPSS and medication results. RESULTS The mean ratio of muscle fiber to collagen in the normal prostate tissue was (3.2 +/- 0.2):1, significantly higher than that of the BPH patients (1: [4.7 +/- 3.1] ) (P < 0.01); that in the BPH patients with BOO was 1: (5.4 +/- 3.7) markedly lower than in those without BOO (1: [2.5 +/- 1.1] ) (P = 0.02); that in the BPH patients with severe prostatic symptoms was 1: (9.1 +/- 2.9), remarkably lower than in those with moderate (1: [5.3 +/- 3.4]) and mild prostatic symptoms (1: [2.8 +/- 1.7]) (P < 0.01); and that in the BPH patients with satisfactory medicinal therapeutic results was 1:(2.3 +/- 1.9), significantly higher than in those with poor therapeutic results (1: [7.6 +/- 4.3]) (P < 0.01). CONCLUSIONS The stromal composition in the prostatic tissue of BPH patients undergoes different degrees of changes. More obvious BPH symptoms and poorer therapeutic results are associated with a bigger proportion of collagens and a smaller proportion of muscle fibers in the prostatic tissue. These changes may play an important role in the development and progression of BPH.