The effects of alloxan-induced diabetes on liver regeneration were investigated. Normal and diabetic rats were sacrificed at eight time periods between 16 hours and 4 weeks following two-thirds partial hepatectomy or sham operation. The results indicate that alloxan-induced diabetes delays but does not prevent liver regeneration following partial hepatectomy. This delay is indicated by a depressed synthesis of RNA, DNA and protein during the first post-operative day and a lack of mitotic figures in the 24-hour sample. In addition, the synthesis of these three cellular constituents did not return to control levels as rapidly in the diabetics. Compared with the sham operated animals, the concentrations of total serum protein remained depressed longer in the diabetic hepatectomized animals. The data indicate that the metabolic alterations associated with alloxan diabetes delay the onset of the regenerative process and prolong the recovery period.