Intragastric administration of the cholera toxin to gnotobiotic mini-pigs results in cyclic morphofunctional alterations of intestinal apudocytes followed by their degranulation, a decrease in their number from 1 to 3 hrs and after 18 hrs, while a slight increase in their number occurred from 3 to 12 hrs. The response of APUD-system cells is similar in large and small intestine. Products of apudocyte secretion may be involved in the diarrheogenic effect of the cholera toxin.