Up to 80% of the rat''s liver can be ex- cised at the 1st stage. The right or left lateral or the median lobe will support life after removal of all other remaining hepatic tissue but the caudate lobe alone is inadequate. Following regeneration of the liver, portions of the liver can be excised by aspiration at the 2d and 3d stages. Prevention of hypoglycemia, hemorrhage and infection insures uniform success of the pro-cedure.