OBJECTIVE To establish sonographic criteria for an early prenatal diagnosis of cloacal exstrophy sequence, an extremely rare congenital malformation. METHODS We assessed all cases of anterior midline abdominal wall defects occurring between November 1, 1986, and May 31, 1993. The charts of those with cloacal exstrophy sequence were reviewed thoroughly. The sonographic findings in each case of cloacal exstrophy sequence were evaluated and compared with the ultrasonic manifestations in other types of anterior abdominal wall defects. RESULTS During the study period, six cases of cloacal exstrophy were diagnosed by ultrasound and confirmed by postnatal autopsy examination. Two of the cases were in different twin gestations. There were 58,288 deliveries during the study period; 665 (1.14%) major malformations were diagnosed ultrasonographically. Identical specific sonographic signs appeared in all six cases of cloacal exstrophy. These included a large infraumbilical, anterior midline defect, a protruding large omphalocele, an absent bladder, a narrowed thorax, a distorted spine, a large sacral meningomyelocele, and bilateral clubfeet. In all cases, the fetal bowel was floating in a large amount of ascites within the omphalocele sac. Polyhydramnios was present in four of the six cases. CONCLUSIONS Based on our sonographic criteria, we believe that an accurate prenatal diagnosis of cloacal exstrophy sequence is feasible, even in the first trimester of pregnancy. These signs distinguish cloacal exstrophy from other types of midline anterior abdominal wall defects, ie, gastroschisis, amniotic band syndrome, and limb-body wall complex (body-stalk syndrome).