Using three pressure transducers, motility of the lower and upper rectum and sigmoid was recorded in 18 healthy and 18 chronically constipated children. The 36 children had a wide range of values for frequency of contractions, duration, amplitude, percent of activity, and surface area under the contraction curves. The mean values for percent of activity and surface area were significantly lower in the constipated than in the control children in all three recording areas (P less than .05). Motility in the constipated children, after 2 months of treatment that included milk of magnesia, showed significant increase when compared with corresponding pretreatment values (P less than .05), and were not different from corresponding values of the control children (P greater than .1). Seven to 12 months and 3 years later, rectal and sigmoid motility remained normal. Three-year follow-up revealed that most of the constipated children were not completely free of constipation and fecal soiling in spite of normal motility. Therefore, it appears that the hypomotility in the untreated patients was the result of the chronic fecal impaction and rectal distension and while it was not the cause of the constipation, it may have contributed to its severity.