We present 2 new patients with the megacystis-microcolon-intestinal hypoperistalsis syndrome (MMIHS), review the literature, and discuss the prenatal diagnosis and treatment. MMIHS, as reported in 43 cases, is usually lethal. Most children die during the first year of life, and only 3 children survived their first year. We report the 6th pair of sibs with the disease. Overall, 17 patients reported have had sibs with MMIHS or the parents were consanguineous; 4 times the parents were first, cousins, confirming that this is an autosomal recessive disorder. The present 2 children, whose parents also were first cousins, were of different sex. They had typical MMIHS with abdominal distension due to pronounced megacystis, hydronephrosis, microcolon, and microileum, involving the distal part of the ileum, malrotation of the gut, and intestinal hypoperistalsis. Neither surgery nor medical treatment was successful and the children died at the age of 19 days and 2 1/2 months, respectively. There is no cure for the disease. However, a new protkinetic drug, Cisapride might be worth trying in these cases. Prenatal ultrasound diagnosis of MMIHS might be possible.