Based on experimental evidence that overexpression of MMP-1 in PCa increases neoplastic cell migration and invasion [19], the present study aimed to measure circulating free MMP-1 concentrations of individuals with PCa and BPH, correcting the results for an important allelic variability identified as predisposing to differential serum enzyme levels [20]. The gene discussed is MMP1; the disease is benign prostatic hyperplasia.