Artificial substitutes for specific functional portions of blood are being developed. Perfluorocarbons have received the most publicity in recent years, and one, Fluosol-DA, is undergoing clinical trials in the United States. The perfluorocarbon emulsions physically dissolve oxygen, which distinguishes them from the chemical binding that occurs in hemoglobin. Fluosol-DA has been shown to transport oxygen in amounts that are probably clinically useful if the patient inspires an atmosphere with increased oxygen. A large clinical trial from Japan suggests that Fluosol-DA is safe to transfuse, although recent work suggests that Fluosol-DA may produce significant pulmonary reactions that can be prevented by steroid administration. These reactions are probably caused by complement activation by an emulsifying agent in Fluosol-DA. Recent applications of Fluosol-DA include use in a resuscitative fluid, use in occlusive vascular disease, an special applications, such as treatment of carbon monoxide poisoning, which take advantage of the solubility properties of perfluorocarbons.