A review of six years' experience with antenatal diagnosis of abdominal wall defects by ultrasound showed its impact to be limited by poor detection rates. Twenty infants with exomphalos and 20 with gastroschisis were recorded but only 25 (63%) were diagnosed antenatally. The ultrasound false negative rate was higher for exomphalos (35%) than for gastroschisis (22%). No difference was detected in the incidence of associated abnormalities, premature gestation, primary closure rate, or mortality between the antenatally and postnatally diagnosed groups for either exomphalos or gastroschisis. Antenatal diagnosis of gastroschisis has little effect on management but allows parental counselling and in utero transfer. The frequency of concomitant abnormalities in exomphalos profoundly affects prognosis and the detection of these is the major role of antenatal diagnosis in this condition. Failure to detect abdominal wall defects by ultrasound may be a reflection of technique or equipment, but some gastroschisis may be of perinatal onset and not detectable antenatally.