Surface and interfacial tensions of symmetric diacyl phosphatidylcholines [(C-n)(2)PC], 6 less than or equal to n less than or equal to 16, at the air-water and perfluorooctyl bromide-water interfaces have been studied. The interfacial tension kinetics were found to be very sensitive to the phospholipid chain length, decreasing by more than an order of magnitude for each pair of -CH2- groups (one per each chain) added. At n > 12, equilibration required more than one day, beyond the accessible experimental range of the Wilhelmy plate method. The surface and interfacial tension data reported in the literature for long-chain phospholipids are argued to be measured under nonequilibrium conditions and, because of this, heavily overestimated. Equilibrium interfacial tensions above the critical micelle concentration varied from 9.8 dyn/cm (n = 6) to 4.0 dyn/cm (n = 12). These values are substantially lower than those observed with conventional nonfluorinated surfactants (e.g., Pluronics or sodium dodecyl sulfate). The lower Ostwald ripening rates observed in phospholipid-stabilized emulsions, in comparison with those stabilized by other hydrocarbon surfactants, can plausibly be explained by the lower equilibrium interfacial tensions found in the phospholipid systems.