We measured the serum gelsolin, actin-modulating protein, levels in five patients after rhabdomyolysis. We observed a tendency of serum gelsolin (83 kDa) to increase during the study period of 11 days. No intracellular gelsolin (80 kDa) was found in the serum, although it is abundant in muscle, and the destruction was severe as judged by other parameters. Serum gelsolin thus behaves differently in rhabdomyolysis than after acute tissue damage in other organs, such as liver necrosis and adult respiratory distress syndrome.