Hirschsprung's disease (HD) is a neurogenic form of intestinal obstruction characterized by a congenital absence of ganglion cells in the submucosal and myenteric plexuses. Acquired aganglionosis (AAG) is a rare condition that may occur following various pull-through procedures for HD. This report describes five boys with acquired aganglionosis. In all cases, the presence of normal ganglion cells was confirmed on review of biopsies of the pull-through segments at the initial operation. The original pull-through procedure included Soave (2), Duhamel (2), and Swenson (1) operations. Three procedures were initially performed at other institutions. Recurrent symptoms including abdominal distention, obstipation, enterocolitis, and failure to thrive developed 7, 11, 12, 18, and 30 months postoperatively (mean, 15.6 months). The diagnosis of AAG was delayed 1.5 to 9 years after the onset of recurrent symptoms. Full column barium enema studies revealed a transition zone or narrow area in the rectosigmoid or descending colon in four children. Repeat full thickness rectal biopsies at 3.0 cm above the anal verge in the pull-through segment confirmed the absence of ganglion cells in each case. Two children (post Swenson and Duhamel) were successfully revised with a Swenson procedure. Two additional children (post Soave and Duhamel) were successfully treated with extended posterior anomyomectomy procedures. The remaining boy now has a preliminary colostomy and is awaiting a second procedure. Vascular compromise of the distal bowel segment at the time of the initial pull-through procedure may contribute to the selective loss of ganglion cells postoperatively as neural tissues are most sensitive to hypoxia.(ABSTRACT TRUNCATED AT 250 WORDS)