We aimed to determine whether rectal distension and/or infusion of bile acids stimulates propagating or nonpropagating activity in the unprepared proximal colon, in 10 healthy volunteers using a nasocolonic manometric catheter (16 recording sites @ 7.5 cm spacing). Sensory thresholds and proximal colonic motor responses were assessed following rectal distension by balloon inflation and rectal instillation of chenodeoxycholic acid. Maximum tolerated balloon volume and the volume that stimulated a desire to defecate were both significantly (p < 0.01) reduced after rectal chenodeoxycholic acid. The frequency of colonic propagating pressure wave sequences decreased significantly in response to initial balloon inflations (p < 0.05), but the frequency doubled after subsequent chenodeoxycholic acid infusion (p < 0.002). Non-propagating activity decreased after balloon inflation; was not influenced by acid infusion, and demonstrated a further decrease in response to repeat balloon inflation. We conclude that rectal chenodeoxycholic acid in physiological concentrations is a potent stimulus for propagating pressure waves arising in the proximal colon and reduces rectal sensory thresholds. Rectal distension inhibits all colonic motor activity.