The surface forces between a crude-oil or its components (asphaltenes, resins, oils) and mineral surfaces have been measured in brine. These force vs. distance curves have been analyzed to understand the role these components play in wettability alteration in oil reservoirs. The forces have been are compared with those obtained from the DLVO theory to explore the nature of interaction and surface characteristics of these components. The surface forces have been measured for different conditions of salt concentration and pH of the intervening brine film.