Abstract. The experiment was performed on sexually mature male Swiss mice to determine the effect of pharmacological doses of glucagon administered over a period of 4 or 8 days on the concentration of triacylglycerols and cholesterol in liver and kidneys of mice selected for fast rate of body weight gain and unselected ones, kept on a high-protein and low-protein diet. On the basis of the results obtained it was concluded that the selection and the diet, as well as glucagon injections, were lowering the content of triacylglycerols and cholesterol in the examined organs of mice, in many cases confirmed in a statistically significant way.