The aim of this study was to analyze the effect of chronic rejection on myoelectric activity of orthotopic small intestine transplants in vivo. Chronic rejection was achieved in orthotopic small bowel allografts (ACI-Lewis) using cyclosporin A for limited immunosuppression. Isogeneic transplants (ACI-ACI) as well as native bowels (ACI) with and without immunosuppression served as controls. Myoelectric activities were recorded after a 12-hr fasting period and analyzed visually. Pacemaker frequencies within grafts were significantly below normal values (group 1: 37; group 2: 31.7; group 3: 37; group 4: 32.3). MMC periods and MMC phases did not show significant differences. The propagation velocity of phase III contractions was elevated in the ileum of grafts undergoing chronic rejection (group 1: 1.79; group 2: 1.59; group 3: 2; group 4: 2.5). In conclusion, fasting motility is altered but preserved in intestinal allografts undergoing chronic rejection. Intrinsic reinnervation from the native duodenum, which is necessary to generate normal pacemaker frequencies, was observed neither in allografts nor in isografts after a three-month period.