This study investigated the retardation effect of tyloxapol on the inactivation of dipalmitoyl phosphatidylcholine (DPPC) surface activity by albumin. Equilibrium and dynamic surface tensions for mixed DPPC/albumin/tyloxapol systems were measured by using a pulsating bubble surfactometer. The inhibitory effect of albumin on DPPC surface activity was sensitive to albumin concentration. By adding 1 ppm albumin to a 1000 ppm DPPC dispersion, the surface activity of DPPC was almost unaffected. However, at higher albumin concentrations, such as 10 or 100 ppm, the DPPC inactivation was greatly enhanced, resulting in much higher equilibrium and dynamic surface tensions. The amount of tyloxapol required for the reversal of albumin inhibition was examined by adding various amounts of tyloxapol to DPPC/albumin mixtures. The inhibition ability of albumin was not affected if lower concentrations of tyloxapol were present in the subphase. However, the albumin inhibition of DPPC surface activity seems to be greatly diminished by increasing tyloxapol concentration to a level greater than 10 ppm, even the albumin concentration was as high as 100 ppm. For the first time, the extent to which tyloxapol may protect DPPC from inactivation by albumin was directly established. The results suggest that the deleterious effect of albumin on the surface tension-lowering ability of DPPC might be reduced or overcome if appropriate amounts of tyloxapol are present.