The milliwatt carbon dioxide laser was used to induce focal lesions and to perform wedge resections in the livers of 75 strain A mice. The procedures were feasible and well tolerated by the mice, with only one postoperative death in the wedge resection group in an early experiment. The hepatic lesions produced by the laser were characterized histologically by an inner area of vaporization, an intermediate area of coagulation necrosis, and an outer rim of cells with variable damage. The lesions healed by fibroblastic proliferation and scar formation with no hepatocytic contribution. The small vessel and bile ductule sealing effect of CO2 laser, together with the sound healing of laser-induced wounds, highlights the usefulness of this modality in liver surgery in general, and suggests its particular application in the treatment of liver trauma and a variety of hepatic focal lesions, neoplastic or otherwise.