Fecal soiling is a common complaint among school-age children. The fecal soiling is often accompanied by chronic constipation and so-called "idiopathic," "functional," or "psychogenic" megacolon, the cause of which is undetermined. The records of all children presenting to a pediatric gastroenterology clinic between 1981 and 1990 with difficult defecation were reviewed to determine the incidence of painful defecation and its relationship to chronic impaction and fecal soiling. There were 227 children; 74 were younger than 36 months of age and 153 were older than 36 months. Of the younger children, 86% presented with pain, 71% with impaction, and 97% with severe withholding. The younger children had painful defecation for a mean of 14 +/- 9 (SD) months before presentation. Of the older children, 85% presented with fecal soiling, 57% with pain, and 73% with fecal impaction, and 96% exhibited withholding; the older children had difficult defecation for a mean of 56 +/- 42 months before presentation. Sixty-three percent of the children presenting with fecal soiling had a history of painful defecation beginning before 36 months of age. Painful defecation frequently precedes chronic fecal impaction and fecal soiling in American children. Early, effective treatment of painful defecation in infancy might reduce the incidence of chronic fecal impaction and fecal soiling in school-age children.