Carbon disulfide is distributed in the body by the bloodstream and is presented as acid-labile and free carbon disulfide in blood. Acid-labile carbon disulfide is a form of bound carbon disulfide recoverable by acid treatment. The objective of this study was to determine which form of carbon disulfide in blood is a useful biological indicator for carbon disulfide exposure. Sprague-Dawley rats were used, and each group received carbon disulfide orally. Free and bound carbon disulfide in whole blood, red blood cells, and plasma was measured by a photoionization detector of gas chromatography. The concentrations of bound carbon disulfide were higher than those of free carbon disulfide in whole blood after administration of carbon disulfide. Acid-labile bound carbon disulfide remained longer than free carbon disulfide in blood for all doses. The concentrations of free and bound carbon disulfide in blood cells were higher than those of plasma. We suggest that acid-labile bound carbon disulfide in blood could be a useful biological indicator for carbon disulfide exposure.