Objective: To analyze the utility of total/free prostate–specific antigen (PSA) and age as predictors of the prostate volume in men with symptomatic benign prostatic hyperplasia (BPH) and no evidence of prostate cancer.Patients and Methods: Total and free serum PSA were determined in 681 patients with normal digital rectal examination and symptomatic BPH using the Hybritech method. Prostate volume was measured by transrectal ultrasound (TRUS). TRUS–guided biopsy was performed in 459 (67.4%) of the patients with a serum PSA >4.0 ng/ml.Results: The relationship with prostate volume was best described in a log linear fashion by free PSA (R2 = 0.367), total PSA (R2 = 0.264) and age (R2 = 0.017). Multiple linear regression demonstrates no significant influence of age. Free PSA was able to predict the individual TRUS prostate volume ±10% in 67% of the patients and ±20% in 91.2% and total PSA in 63 and 90.9%, respectively.Conclusion: Prostate volume is strongly related with free and total PSA. Both determinations would be able to predict the TRUS prostate volume ±20% in more than 90% of the patients.