OBJECTIVE To evaluate the relationship between prostate specific antigen (PSA) and prostate volume (PV) in Korean men, as PV is a key predictor of both disease progression and response to medical therapy in patients with benign prostatic hyperplasia (BPH), and PSA has been suggested as a proxy marker to estimate the total PV, mainly in Caucasians. METHODS From 1999 to 2004, men aged 50-79 years with lower urinary tract symptoms (LUTS) and BPH were enrolled into this multicentre study. The analyses included 5716 patients presenting to 11 medical centres with LUTS (International Prostate Symptom Score >8, peak urinary flow rate <15 mL/s); they had a mean age of 64.3 years, mean baseline PV of 36.9 mL, and mean baseline PSA level of 2.2 ng/mL. Men with a baseline PSA of >10 ng/mL were excluded, to reduce the likelihood of including occult prostate cancer. A biopsy was taken in those with suspicious findings on a digital rectal examination or serum PSA level of >4 ng/mL, to exclude prostate cancer. Receiver operating characteristic (ROC) curves were constructed to evaluate the ability of serum PSA to predict threshold PV in men with BPH. RESULTS The PV and serum PSA level had an age-dependent log-linear relationship, the strength of which increased with age. The ROC curve analysis showed that PSA had good predictive value for various prostate volume thresholds (30, 40 and 50 mL). CONCLUSIONS The PSA-PV relationship in Korean men is similar to that in Caucasians, but Korean men have a slightly lower PSA level and a smaller PV than Caucasians. The approximate age-specific criteria for detecting Korean men with a PV of >40 mL were a PSA level of >1.3 ng/mL, >1.7 ng/mL and >2.0 ng/mL for men with BPH in their sixth, seventh and eighth decade, respectively.