Regeneration, function, and maintenance of integrity were studied in five groups of hemihepatectomized dogs with varying hemodynamic inflow and one group with intact livers but differentially ligated inflow to each half. Regeneration was similar in dogs with both hepatic arterial and portal venous supply, compared with those with portal vein supply only, but was minimal in livers supplied by artery only. This was not increased with perineurectomy. Augmentation of flow in this latter group, utilizing a portarenal transposition, resulted in significant increase in liver mass and size on scan and a healthier course. Atrophy, as distinct from lack of regeneration, is solely dependent upon adequacy of total liver blood flow and not any trophic substance or type of flow. This concept is extended to the auxiliary transplant model and its possible use as temporary hepatic support.