Osteocalcin is a vitamin K dependent and bone specific protein which plays an important role in the regulation of bone and calcium metabolism. In this study, we evaluated the relationship between the C298T polymorphism in the osteocalcin gene and bone mineral density (BMD) in Korean young men and their interaction with physical activity. BMDs of the femoral neck and lumbar spine were measured using dual energy X-ray absorptiometry, and the C298T polymorphism in the osteocalcin gene determined using polymerase chain reaction (PCR)-HindIII restriction fragment length polymorphism (RFLP) method. We did not observe any significant differences in the femoral neck and lumbar spine BMDs across genotypes of this polymorphism in controls, athletes or combined groups, respectively (P>0.05). Therefore, our data suggest that the C298T polymorphism in the osteocalcin gene is not a suitable genetic marker for the susceptibility to BMD.