Intake of thioacetamide in drinking water causes liver cirrhosis in rats, which exhibit many changes similar to human disease. Nucleotides play an important part in major cellular functions, and recent studies suggest that dietary nucleotides may be considered 'semi-essential' nutrients in situations when an inadequate dietary supply may affect the growth of tissues with a rapid turnover rate. The aim of this study was to assess the effect of dietary nucleotides on lesions in thioacetamide-cirrhotic rats, and to calculate the proportion of mono and binucleated hepatocytes in different experimental groups. Rats were given cirrhosis by oral intake of thioacetamide in the drinking water (300 mg/l) for four months. One group was treated with a standard nucleotide free diet, and another group was treated with the same diet supplemented with 250 mg of nucleotides per 100 g of diet for one and two weeks. A striking reduction (mean (SEM)) in the proportion of binucleated cells was seen in thioacetamide-cirrhotic rats (4.8 (1.3) v 21.4 (1.0)), showing a change in the mitotic mechanism in focal lesions. Cirrhotic rats that consumed a semipurified diet supplemented with nucleotides during two weeks showed considerable histological regeneration of the injured liver. These animals had significantly higher proportion of binucleated cells than did animals at the beginning of the recovery period (8.2 (1.2) v 4.8 (1.3)). In the second week of recovery, both types of diet (F = 5.54, p < 0.05) and the previous administration of thioacetamide (F = 142.82, p < 0.001) had significant effects on the percentage of binucleated hepatocytes.