The motility of the gastroduodenal wall, movement of gastric contents, and velocity curves of transpyloric flow can be synchronously visualized by duplex sonography. In eight healthy individuals, 18 +/- 6 (mean +/- SD) peristaltic cycles per person in response to the ingestion of 500 mL of meat soup were recorded. Coordinated antroduodenal contractions were seen in 67% of the cycles. Two types of duodenogastric reflux were observed. One type occurred in the middle of the peristaltic cycle (midcycle reflux), whereas the other followed immediately after antegrade flow at the end of the cycle (end-cycle reflux). End-cycle reflux was significantly more frequent in conjunction with coordinated (70%) than with uncoordinated (17%) antroduodenal contractions (P less than 0.005). Thus, in the fed state, a short gush of duodenogastric reflux normally precedes the peristaltic closure of the pylorus.