A retrospective study of 20 multiple pregnancies and a prospective study of 13 multiple pregnancies were done to determine the accuracy of ultrasound in the diagnosis and dating of multiple pregnancy and in predicting intrauterine growth retardation (IUGR). The diagnosis of 1 multiple pregnancy in our study was missed. In another case triplets were erroneously diagnosed as a twin gestation. Fetal biparietal diameter correlates well with gestational age, particularly when the characteristic growth pattern of twins is taken into account. Ultrasound was noted to be of only limited use in antenatal diagnosis of IUGR, with a significant number of false positives and false negatives noted.