Background/Purpose: Constipation is a major complication in patients who have undergone posterior sagittal anorectoplasty (PSARP) operation for a high anorectal malformation. Overflow incontinence is the main cause of fecal soiling in these patients. The aim of this study was to outline the natural history of constipation in patients with high anorectal malformations and relate this to the functional outcome at the end of the patient's growth period. Methods: The study group consisted of 22 pubertal or postpubertal patients (median age 15; range, 13 to 25) with high or intermediate anorectal malformations repaired by PSARP procedure. The patients have been followed-up since birth. Constipation was defined as a need to use medical treatment or diet to ensure bowel emptying. Continence was classified as follows: grade 1, no soiling in any circumstances; grade 2, staining less than once a week, no fecal accidents; grade 3, staining more than once a week, no fecal accidents; grade 4, daily soiling or accidents, need for regular enemas, or the antegrade colonic enema procedure. All patients underwent anorectal manometry and magnetic resonance imaging of the spine and spinal cord. Results: At the time of the study 2 (9%) of the 22 study group patients had constipation, but 15 (68%) had been constipated before puberty. Eleven patients (50%) were fully continent (grade 1) without constipation. Six of those had a history of constipation associated soiling. Three patients (14%) had occasional staining (grade 2) and no constipation. Two of them had been constipated with significant soiling before the onset of puberty. In the 5 (22%) patients with frequent staining (grade 3) the degree of soiling had decreased after the disappearance of constipation. Two of the 3 patients with poor outcome (grade 4) require regular enemas for recalcitrant constipation. Spinal cord anomalies were detected in 4 and abnormal sacrum in 15 patients. Of the anorectal manometric parameters, only the force of voluntary sphincter squeeze correlated with the functional result. Conclusion: In the majority of patients who underwent PSARP procedure for high anorectal malformation, constipation disappears at adolescence, and this is associated with improved fecal continence outcome. J Pediatr Surg 36:1218-1221. Copyright © 2001 by W.B. Saunders Company.