Perfluorocarbon compounds (PFC's), well known in industry and of late as synthetic oxygen carriers, have a wide range of significant applications in diagnostic imaging. Their enhancement effect is detectable by ultrasound and magnetic resonance and if radiopaque, such as perfluoroctylbromide (PFOB), by standard radiography and computed tomography (CT). We have utilized PFOB as a CT contrast agent to enhance the blood pool, and as both a CT and an ultrasound contrast agent to enhance the liver, spleen, abscesses, infarctions, and tumors or any tissue where inflammatory cells can be found. PFC's, except for the echogenic enhancement of the vascular space on their first pass to the lung, do not enhance the blood pool on ultrasound. Otherwise, ultrasound applications are similar to those observed for CT. Fluosol, which was available for human trials, is not radiopaque and therefore served as an ultrasound contrast agent. In a preliminary clinical trial, Fluosol produced tumor enhancement in man at 1.6g/kg allowing the visualization of previously missed lesions and liver and spleen enhancement at 2.4g/kg allowing the visualization of previously missed non-enhancing lesions. Perfluorocarbon toxicity seems to be related to the constituents of the emulsion rather than the perfluorocarbon itself. Improvements in the emulsifier and emulsification technology has yielded stable emulsions at high concentrations and low toxicity.