After a Roux-en-Y gastrojejunostomy, patients frequently complain of abdominal pain, fullness, nausea, and vomiting. This so-called Roux-en-Y syndrome is caused by slow gastric emptying, Roux-limb stasis, or both. The pathogenesis of these transit disorders is unknown. The aim of the present study was to investigate whether slow gastric emptying and Roux-limb stasis can be attributed to motility disturbances in the Roux limb. Thirty-seven patients with a Roux-en-Y gastrojejunostomy after partial gastrectomy were studied, 26 of whom had the Roux-en-Y syndrome and 11 who did not. Gastrojejunal transit was evaluated by radionuclide studies, and motility in the Roux limb was studied by manometry. Thirteen patients had slow gastric emptying, and 14 had stasis in the Roux limb. Slow gastric emptying, Roux-limb stasis, or a combination of both was found in 20 of 26 symptomatic patients and in only 4 of 11 asymptomatic patients (p < 0.05). The basic motor patterns, the interdigestive motor cycle, and the fed state were present in most patients. However, motility disturbances were present in 34 of the 37 patients. Motility disturbances were observed significantly more frequently in patients with symptoms than in those without, and also in patients with Roux-limb stasis than in those without, but no relation was found between motility disorders and slow gastric emptying. Aberrant propagation of the migrating motor complex and the absence of the fed state were the only motility disorders that were not observed in patients with normal Roux-limb transit. Of the various recorded motility disturbances, these two probably represent the more serious motility disturbances. The results of our study indicate that Roux-limb stasis is caused by motility disorders in the Roux limb. They also indicate that Roux-limb stasis is not responsible for slow gastric emptying, since there is no correlation between motility disorders in the Roux limb and slow gastric emptying.