Sonograms of fetuses at risk for congenital lethal osteogenesis imperfecta (osteogenesis imperfecta type II) were retrospectively reviewed blindly and correlated with pregnancy outcomes. Six of eight cases of type II osteogenesis imperfecta were correctly diagnosed with use of the proposed criteria of multiple fractures, demineralization of the calvaria, and femoral length more than 3 standard deviations below the mean for gestational age. The two cases not diagnosed had sonographic abnormalities but did not meet all three criteria. Among 18 pregnancies genetically at risk for the disease but with normal outcomes, all sonograms were normal, meeting none of the proposed criteria. Among an additional 25 fetuses with osteochondrodysplasias, no case satisfied all three of the proposed diagnostic criteria. With use of strict standards for the diagnosis of type II osteogenesis imperfecta, this disease can be distinguished from other fetal skeletal abnormalities. In a pregnancy at risk for recurrence of osteogenesis imperfecta, a normal sonogram after 17 weeks excludes this lethal condition.