Novel emulsions containing iodinated fluorinated radiopaque (IFR) molecules were prepared and evaluated as injectable contrast agents with prolonged intravascular persistence. Various stable IFR/egg yolk phospholipid emulsions were produced, heat-sterilized, and tested as to their radiopacity, shelf-stability and in vivo tolerance. No significant change in mean particle sizes was observed over a 3-month storage period at 40 degrees C. Intravenous injection of an emulsion of a 0.39 g/kg bw dose of a typical IFR, C6F13CH = CIC6H13 (F6H6IE) in rabbits led to high contrast in the liver and spleen. The same radiopacity of the liver was achieved with 7 times less IFR than perfluorooctyl bromide. Histological examination after 24 h, and blood analysis after 24, 48 h and 7 days, demonstrated normal functioning of the liver, even when high concentrations of IFR were present. The neat IFR was tolerated i.p. in mice at a 45 g/kg bw dose. Emulsified IFR was tolerated in rats and mice i.v. at a 8 g/kg bw dose. The iodinated fluorinated molecule tested appears promising for the formulation of new contrast agents for diagnosis.