We studied morphofunctional changes in the liver parenchyma of young male Wistar rats after methionine administration. The experiments were performed on 24 male 3 months old Wistar rats. Animals of the experimental group, in addition to the standard diet, daily for 21 days received methionine at a dose of 250 mg/kg body weight. Histological preparations were prepared from liver tissue by a standard technique. Morphometry was performed on digital images using the computer program «Image J». Succinate dehydrogenase activity and protein concentration were determined in the suspension of hepatocyte mitochondria. It was revealed that 21-day administration of methionine led to hypertrophy of the hepatocyte nucleus, an increase in the nuclear cytoplasmic ratio (by 13 %), the number of binuclear hepatocytes (by 94 %), the nucleolus in the cell nucleus (by 17 %) and the relative area of the sinusoid network (by 50 %). The increase in succinate dehydrogenase activity and protein concentration was revealed in the suspension of hepatocyte mitochondria of the experimental rats. This indicated an increase in the mitochondria energy potential and protein-synthetic activity. The administration of methionine to young rats was accompanied by the appearance of morphological and functional signs of the liver parenchyma synthetic and regenerative processes activation.