The purpose of this study was to determine the utility of jejunal manometry in evaluating patients having partial small intestinal obstruction or the pseudoobstruction syndrome. We studied 10 healthy volunteers, 9 patients with documented mechanical obstruction, and 3 patients with chronic intestinal pseudoobstruction during fasting and for 2 h after a 650-kcal meal. Contractile activity, especially during phase 2, was extremely variable in all individuals studied. After the meal, the most striking finding in mechanical obstruction was the regular occurrence of clustered contractions. These were defined as 3-10 regular contractions, occurring 1 per 5 s, preceded and followed by at least 1 min of absent motor activity. The associated periods of quiescent motor activity may account for the unexpectedly reduced frequency and motility index in obstructed patients compared with normal subjects after the meal. Two different contractile patterns occurred in patients with pseudoobstruction. Before and after the meal, infrequent and low-amplitude contractions occurred in 2 patients, and multiple, aborally migrating, clustered contractions occurred in the other patient with pseudoobstruction. Manometric abnormalities occur in both mechanical obstruction and pseudoobstruction. However, the technique is probably not more sensitive than radiologic procedures, and the abnormalities that are detected by manometry are not specific. Some of the same motility changes occurred in both disorders.