In the present study histochemical parameters of the rat gastric endocrine cells were followed up in the course of 24-h autolysis, and their ultrastructure was studied during autolysis lasting for 60 min. The autolysis occurred at 37 degrees C. In the light microscope, with the histochemical methods applied, only EC, ECL and G cells could be identified during the one-hour autolysis. With the autolysis proceeding for 6 and 12 h, only argyrophil method according to Grimelius (1968) enabled visualization of gastric argyrophilic cells. After 24 h of autolysis, none of the methods applied (not even the Grimelius method) proved to be adequate for successful demonstration of the gastric endocrine cells. In the course of 60-min autolysis, electron microscopic examination provided identification of the EC, ECL, AL, D1, and G cells with the characteristical ultrastructural appearance of granules. The granules of the endocrine cells (G cells included) were found to be considerably resistant to autolysis. The effect of 60-min autolysis did not induce granule "emiocytosis" or dissolution of granule content. Autolysis exceeding five minutes resulted in damage of the mitochondria of different degrees and in dilatation of the profiles of endoplasmic reticulum (particularly in G and AL cells). The results obtained in the present study demonstrate the feasibility of in vitro experimental stimulation since the endocrine granules have proved to be resistant to the effects of simultaneously developing autolysis.