Leptin is a hormone produced and secreted mainly by adipocytes, but also by other tissues such as placenta, brain, mammary, and pituitary glands. The gastric epithelium has also been reported as a source of leptin in mammals. In this study we examined the presence of leptin in the stomach of non-mammalian vertebrates (trout, frog, lizard, and snake). Immunolabeling for leptin was found in the oxyntic-peptic cells of the frog and the two reptilian species studied, but not in the trout. In the trout and the lizard leptin immunoreactivity was also detected in scattered cells presenting the typical features of endocrine cells. In the trout, the frog and the snake, in addition to the epithelium, leptin immunostain was found in elements of the enteric nervous system that were also positive for VIP.