Objective - to identify the localization, percentage and morphometric characteristics of calbindin (CB) and calretinin (CR)-immunoreactive (IR) neurons in the methasympathetic intramural ganglia of the myenteric (MP) and submucous plexus (SP) of the large intestine of rats of different age groups. Material and methods. Thick sections of the transverse colon of Wistar rats aged 1, 10, 20, 30, 60 days and 2 years were studied by immunohistochemical and morphometric methods. Results. CB-IR and CR-IR neurons were demonstrated in rats of all studied age groups. In the MP, the percentage of CB-IR and CR-IR neurons on the 10th day of life was significantly greater than after birth, and did not change in the older groups. In the SP of newborn rats, CB was not detected (it was demonstrated only from the 10th day), and CR was detected in 72,0±2,52 % of neurons. A significantly higher percentage of CB-IR and CR-IR neurons was detected in 2-month-old and older rats. The average cross-sectional area of CB-IR and CR-IR cel