OBJECTIVE We prospectively compared changes in function between colonic J-pouch and straight anastomoses from 1 to 5 years after low anterior resection for rectal cancer. METHODS At 1, 3, and 5 years after surgery, functional outcome was compared between 48 patients with J-pouch reconstruction (J group) and 51 with straight anastomosis (S group), using a 17-item questionnaire (overall best, 0; overall worst, 26). Reservoir function was evaluated manovolumetrically. RESULTS At 5 years, patients with ultralow anastomoses (< or =4 cm from anal verge) had fewer bowel movements during day or night, and less urgency and soiling in the J than S group. At that time, patients with low anastomoses (5 to 8 cm above the verge), had fewer bowel movements at night and less urgency in the J than S group. Manovolumetric results were better in the J than S group for both anastomotic levels. Functional scores improved significantly over time for both anastomotic levels, especially in the S group. Mean scores with ultralow anastomoses were J-group, 5.6 at 1 year vs. 5.3 at 3 years (P = 0.0304) vs. 3.7 at 5 years (P < 0.0001); and S group, 10.2 at 1 year vs. 9.6 at 3 years (P = 0.0063) vs. 7.3 at 5 years (P < 0.0001). Mean scores with low anastomoses were J group, 3.4 at 1 year vs. 3.1 at 3 years (P = 0.0052) vs. 2.1 at 5 years (P = 0.0003); and S group, 5.2 at 1 year vs. 3.8 at 3 years (P < 0.0001) vs. 2.7 at 5 years (P < 0.0001). Manovolumetric results improved overtime in both groups. CONCLUSIONS Functional outcome improved in the J and especially the S group over 5 years. However, function was better in the J than S group at all time points.