Background and Purpose: Constipation is one of the major sequelae in patients after correction of anorectal anomalies (ARAs). The aim of the present work has been to assess the colonic transit time,using radioisotope scintigraphy,in patients operated for ARA and experiencing constipation in the follow-up. The results were compared with transit time from children with true functional constipation. Methods: Twelve or 32 patients operated for ARA during the period 1994-2003 experienced mild or severe constipation (6 with high or intermediate form of ARA and 6 with low type) at follow-up. The mean age of this group was 5.8 years. Eighteen patients,mean age 6.7 years,with true functional constipation were studied as well. Colonic transit times were investigated using radioisotope scintigraphy. Normal values for colonic transit time were derived from historical controls. Radioisotope diethylenetriamine pentaacetic acid labelled with indium 111 was administered orally to determine a segmental colonic transit. Images of the abdomen have been taken at 6,24,48,and again at 72 hours,if radioactivity was not cleared from the colon. To quantify colonic transit,we calculated the geometric centre (GC) dividing the colon into anatomic regions. Results: According to normal controls,2 different type of delayed transit can be observed: (a) slow-transit constipation if GC at 48 hours is less than 4.1; (b) functional rectosigmoid obstruction (FRSO) if GC at 48 hours is 4.1 or more but less than 6.1 at 72 hours. Patients with functional constipation were divided into 2 groups: (a)-slow-transit constipation in 12 patients with a GC at 48 hours of 3.7 ± 0.5; (b) FRSO in 6 patients with a GC of 4.7 ± 0.04 and 5.02 at 48 and 72 hours,respectively. Patients operated for high ARA had values characteristic of FRSO with GC at 48 hours of 5.1 ± 0.8 and 4.75 ± 0.5 at 72 hours. In low ARA,the transit times were similar to the ones observed in patients with high ARA at 48 hours with a GC of 4.9 ± 0.5. Conclusions: Patients with ARA frequently have functional sequelae in the postoperative period such as constipation. According to our results,constipation seems to be secondary to segmental motility disorders limited to the rectosigmoid area,similar to constipated children with FRSO. No evidence of more gener-alised motility disturbance,as previously postulated,could be recorded. Background and Purpose: Constipation is one of the major sequelae in patients after correction of anorectal anomalies (ARAs). The aim of the present work has been to assess the colonic transit time, using radioisotope scintigraphy, in patients operated for ARA and experiencing constipation in the follow-up. The results were compared with transit time from children with true functional constipation. Methods: Twelve or 32 patients operated for ARA during the period 1994-2003 experienced mild or severe constipation (6 with high or intermediate form of ARA and 6 with low type) at follow-up. The mean age of this group was 5.8 years. Eighteen patients, mean age 6.7 years, with true functional constipation were studied as well. Colonic transit times were investigated using radioisotope scintigraphy. Normal values ​​for colonic transit time were derived from historical controls. Radioisotope diethylenetriamine pentaacetic acid labeled with indium 111 was administered orally to determine a segmental Collected transit. Images of the abdomen have been taken at 6,24,48, and again at 72 hours, if radioactivity was not cleared from the colon. Results: According to normal controls, 2 different types of delayed transit can be observed: (a) slow-transit constipation if GC at 48 hours is less than 4.1; (b) functional rectosigmoid obstruction (FRSO) if GC at 48 hours is 4.1 or more but less than 6.1 at 72 hours. Patients with functional constipation were divided into 2 groups: (a) -slow-transit constipation in 12 patients with a GC at 48 hours of 3.7 ± 0.5; (b) FRSO in 6 Patients with a GC of 4.7 ± 0.04 and 5.02 at 48 and 72 hours, respectively. Patients operated for high ARA had values ​​characteristic of FRSO with GC at 48 hours of 5.1 ± 0.8 and 4.75 ± 0.5 at 72 hours. In low ARA, the Transit times were similar to the ones observed in patients with high ARA at 48 hours with a GC of 4.9 ± 0.5. Conclusions: Patients with ARA frequently have functional sequelae in the postoperative period such as constipation. According to our results, constipation seems to be secondary to segmental motility disorders limited to the rectosigmoid area, similar to constipated children with FRSO. No evidence of more gener-alized motility disturbance, as previously postulated, could be recorded.