Apocrine glands of the anal sacs in cats (Felis silvestris f. catus) were examined by transmission and scanning electron microscopy. The secretory cells exhibit a typical equipment with organelles that varied according to the season as well as the animal’s sex and state of reproduction. This can be mainly explained by seasonal differences in secretory activity. The cytological dynamics observed are, particularly, related to the smooth endoplasmic reticulum, which, for the first time, can be demonstrated in its crystalloid form in apocrine gland