The effect of nitric oxide (NO) synthase inhibition on the gastric emptying of nutrient and nonnutrient meals was investigated in nine dogs. The inhibition of NO synthase delayed the gastric emptying time of both nutrient and nonnutrient meals, but the percentage delay of nutrient meals was significantly greater than that of nonnutrient meals. The inhibition of NO synthase during the emptying of nonnutrient meals enhanced mainly the amplitude of antral, pyloric, and distal duodenal contractions. However, NO synthase inhibition during the emptying of nutrient meals stimulated several spatial and temporal parameters of gastropyloroduodenal contractions. We conclude that NO is one of the neurotransmitters of intestinal feedback that regulates the gastric emptying of both nutrient and nonnutrient meals. The nature and intensity of intestinal feedback by the stimulation of both chemo- and mechanoreceptors by nutrient meals is different from that by the stimulation of mechanoreceptors only by the nonnutrient meals.