This work describes the patterns of changes in activity of gamma-glutamyltransferase (GGT) in tissues of various liver lobes (caudate, mastoid, right outer, left outer, left inner, and square) of gray giant rabbits at different phases of postnatal ontogenesis. The enzyme activity was determined by spectrophotometric method in the scientific laboratory of Chuvash State Agrarian University. It was revealed that rabbits are born with different enzyme activities in the studied liver lobes, and the intensity of age-related changes of GGT activity in the studied rabbits’ periods of life in the tissues of liver lobes is diverse, which is connected with change of vegetable feed composition and with unequal need for enzyme participation in metabolic processes in the body tissues during the studied early postnatal period. The most intense changes in enzyme activity with age of rabbits occur at colostrum-milk phase in the square lobe; as for the first phase of milk nutrition - in the right and left outer lobes; the third phase of milk nutrition - in the left inner and in the square lobes; in the second phase of transitional nutrition - in the left inner lobe. Stabilization of GGT activity does not happen by the age of two months.