Storage stable fluorocarbon emulsions having a continuous aqueous phase and a discontinuous fluorocarbon phase, in which the fluorocarbon phase comprises a major amount of a first fluorocarbon or fluorocarbon mixture, and a minor amount of a second fluorocarbon or fluorocarbon mixture, in which the second fluorocarbon has a molecular weight greater than that of the first fluorocarbon and the second fluorocarbon includes a lipophilic moiety in its structure, whereby the second fluorocarbon serves to promote particle size stability in the emulsion while simultaneously providing favorably short organ retention times when administered to animals in vivo.