Abstract: The purpose of this study was to describe the distribution of serum prostate specific antigen (PSA) and to determine age-specific reference range in a population of Persian men. Venous blood samples were taken from 287 men, from Gorgan located in the North of Iran, South-East of Caspian Sea, aged 15≥80 year. The serum PSA levels was measured using Enzyme-linked Immunosorbant-Assay (ELISA) technique and age-specific range for PSA level was determined. The serum prostate-specific antigen level for six age group of 15-40 years, 41-50 years, 51-60 years, 61-70 years, 71-80 years and >80 years were mainly in the range of 0-2.5 ng mL-1, for 76.6%, 2.6-4 ng mL-1 for 9.1% and as whole 85.7% of all men in this study had ≤4 ng mL-1, 8.7 and 5.6% all men of six age group had PSA level of 4.1-10 ng mL-1 and >10 ng mL-1, respectively. The findings of present study indicated that a large proportion (76.6%) men in this region have a lower PSA level of 0-2.5 ng mL-1 and only 9.1% of men have PSA level of 2.6-4 ng mL-1. It is therefore concluded that acceptable reference range of 0-4 ng mL-1 for PSA level require further reassessment.