Male thoraco-omphalopagus conjoined twins were evaluated systematically with respect to visceral joining. Cardiac studies included electrocardiography, echocardiography, and a dynamic radioactive heart scan. No union was found. Liver union was demonstrated by scanning and angiographic studies. No communication between the gastrointestinal tracts was found, and no other major anomalies were discovered. When the twins were approximately 3 months of age, surgical separation was performed. A common pericardium, two separate hearts, and a union of the liver were found. Prosthetic sheeting was used to close the pericardium and the thoracic-abdominal defects in both. In one, primary skin closure was possible. In the other silicone rubber sheeting was used to close a large skin defect in the chest. Both have done well over a follow-up period of 14 months. One is larger than the other, but the growth rate of both has improved in the last 6 months.