Direct measurements of interaction forces between a-alumina surfaces with coadsorbed anionic surfactant (sodium dodecyl sulfate (SDS) or lithium perfluorooctanesulfonate (LiFOS)) and nonionic polymer poly(vinylpyrrolidone) (PVP) at pH 3.5 are carried out by colloidal probe atomic force microscopy. In aqueous SDS solutions, the strength of interaction forces is found to depend on the initial SDS concentration, whereas in PVP solutions, the electric double layer interaction is completely screened due to the flat conformation of PVP on alpha-alumina. The interaction forces are dramatically different for the coaddition of SDS and PVP: electrostatic repulsion is observed above the critical aggregation concentration, and virtually no steric hindrance due to adsorbed polymer chains can be detected. These coaddition effects are attributed to the flat conformation of the adsorbed PVP and the formation of SDS-PVP surface complexes as confirmed by surface tensiometry. The LiFOS-PVP system exhibits characteristics similar to those of the SDS-PVP system, except that the repulsion between adsorbed LiFOS layers is remarkably weak at concentrations above its critical micelle concentration. The effects of sequential addition of SDS and PVP are also investigated.