Background: Clinically, many attempts at small intestinal transplantation in humans have been performed. Although little is known about the long term results on motor function of the transplanted small intestine, small intestinal motility should continue to be one of the most important issues in small intestinal transplantation. Study design: We investigated small intestinal motility 10 to 15 months after orthotopic small intestinal transplantation in rats. Six male Lewis rats underwent orthotopic jejunoileal transplantation. Intestinal myoelectric activity was recorded in the rats using Ag-AgCl bipolar electrodes. Six age-matched Lewis rats were also studied as controls. Results: The cycle length of migrating myoelectric complexes (MMCs) in the transplanted jejunum (T-J), recipient's jejunum (R-J), and jejunum of the control rat (C-J) groups were 16.2±3.8 min, 13.7±1.4 min, and 1l.1±0.3 min, respectively. In the C-J and T-J, a respective 98.1% and 96.5% of phase IIIs at the distal site occurred following the phase IIIs at the proximal site within 20% variation of the MMC period. However, between the R-J and T-J, only 31.0% of phase IIIs occurred within 20% variation of the MMC period. Coordination of the MMCs between the recipient and transplanted intestine did not occur at 10 to 15 months after the operation in the rat. During fasting, MMCs were clearly identified in the small intestine of both control and transplanted rats. Feeding interrupted the periodic activity, and irregular spike activity was observed along the entire small intestine, though conversion of the fasting to the fed pattern was delayed by about a minute in the graft intestine. The slow wave frequencies in the T-J, R-J, and C-J were 32.8±2.7 cpm, 36.3 ± 2.7 cpm and 36.3 ± 2.4 cpm, respectively. Conclusion: These results suggest that the motility of the transplanted small intestine is mostly preserved, however, temporal coordination of the MMCs across the anastomosis did not occur after transplantation.