Following 70% hepatectomy on rats the galactose elimination capacity, taken as a measure of the cytosolic liver function, was reduced from 2.55 +/- 0.48 to 1.27 +/- 0.19 (mean +/- SEM) mumol/min. Six hours later it was restored to control values. The prothrombin index, representing the function of the endoplasmic reticulum, was reduced from 1.13 +/- 0.02 to 0.34 +/- 0.02 (arbitrary units) after 12 h, and it was restored after 96 h. The rapid normalization of the initial fall in the capacity to metabolize galactose reflects a two- to three-fold increase of the galactose metabolizing capacity of the remaining liver. This study demonstrates that liver functions are dissociated in time following 70% hepatectomy in the rat, and that the galactose elimination capacity is restored before regeneration can compensate for the loss in liver cell mass.