The experiment was carried out on 30 56‐day old mice selected during 12 generations for feed efficiency and 30 unselected mice. Measurements were made of beta‐glucuronidase; beta‐galactosidase; beta‐glucosidase; N‐acetyl‐beta‐glucosaminidase; acid phosphatase; alanyl aminopeptidase; cathepsin D; lysosomal esterase and lysosomal lipase. The results suggest that the selected animals had higher activities of the lysosomal enzymes in comparison with unselected ones.