The rates of degradation of liver cell plasma membranes from control and partially hepatectomized rats were investigated by a single isotope administration procedure utilizing L-[3H]fucose as a precursor. The label was incorporated maximally into normal plasma membranes at 2 to 4 h after intravenous injection. At 4 h, L-[3H]fucose activity was 8-fold more abundant in membrane protein than in total liver protein. Paper chromatography of neutral sugars liberated by acid hydrolysis of the plasma membranes indicated that greater than 90% of the recovered radioactivity was in the form of fucose. After partial hepatectomy, the wet weight of the right lateral liver lobe increased linearly during a 4-day postoperation interval. In addition, the specific activity of plasma membrane alkaline phosphatase was elevated to a level that remained 3 to 4 times higher than that of the control membranes. However, there was not much difference between the mean rates of degradation of the labeled plasma membrane components from the control and regenerating livers. The apparent half-lives were 33 and 40.8 h, respectively. This suggests that the dissociation of fucose-containing components from the plasma membrane is not markedly altered during the process of rapid compensatory liver growth.