The serum copper parameters were evaluated in 41 male trained runners and in a control group of 24 male subjects engaged in normal physical activity. In the runner group lower serum copper concentrations, lower serum ceruloplasmin biological activity, and higher serum ceruloplasmin levels were found compared with the control group. Reduced serum copper levels may affect the ceruloplasmin biological activity, even if the serum ceruloplasmin levels are higher. The results suggest that more attention should be paid to serum copper and ceruloplasmin in athletes.