&NA;An immunoperoxidase staining method was used to study specific immunoglobulin‐containing cells in the intestinal mucosa of children who presented with features suggestive of Hirschsprung's disease. No evidence was found to substantiate the hypothesis of an immunologic component in the etiology of Hirschsprung's disease. The megacolon in this condition had an increased proportion of IgG‐containing cells and a reduced proportion of IgA‐containing cells when compared with normal and unobstructed colon; this may be a reflection of an abnormal mucosal immune defense leading to susceptibility to the enterocolitis found in Hirschsprung's disease. Numerous lipofuscin‐bearing macrophages were seen in the colonic mucosa of children with anal stenosis who were given anthraquinone laxatives for varying periods. The possibility that this represents an early stage of melanosis coli, as well as the likelihood of anthraquinones contributing to the pathogenesis of acquired megacolon, are considered.