We have documented the clinical, radiologic, and autopsy findings of 2 fetuses with atelosteogenesis type I, aged 22 and 17 weeks. This rare autosomal dominant lethal skeletal dysplasia is caused by mutation in the FNLB gene. The 17-week-old fetus had some features of atelosteogenesis type II, notably "hitchhiker thumbs," a cleft palate, and midfacial flattening. The histologic demonstration of giant cells in the growth plate cartilage confirmed the diagnosis of atelosteogenesis type I in both fetuses, thereby facilitating accurate prediction of recurrence risks for the parents of the affected fetuses. Autopsy findings included tracheal narrowing and stenosis with pulmonary hypoplasia in both fetuses. Renal microcysts and abnormal branching of the pancreatic duct were also present in 1 of the fetuses, and malrotation of the caecum and retinal dysplasia involving the optic nerve were identified in the other. Postmortem and histologic investigations play an important role in the elucidation of the genetic micromelic skeletal disorders that are lethal in the fetus and neonate.