A case of megacystis-microcolon-intestinal hypoperistalsis syndrome (MMIHS) is presented. There were important findings: a urachal remnant and a brother with prune belly syndrome (PBS). After a review of the literature, many common characteristics of MMIHS and PBS are described: flaccid abdomen, dilatation of the urinary tract, intestinal malrotation, cryptorchidism, urachal remnants and familial incidence. MMIHS and PBS may be manifestations of the same underlying process.