This review focuses on the macroscopic phenomena that can be used to assess effective wetting, especially the use of contact angles to quantify wetting conditions in the presence of brine and crude oil or on surfaces that have previously been exposed to brine and crude oil. Reservoir wettability has long been a puzzle. Wetting is almost certainly changed during all but the most careful core recovery processes and there is no guarantee that it can be preserved or recreated in the lab. Thus a great deal of effort has been directed at trying to understand reservoir wetting at a more fundamental level. The most important recent advances have demonstrated that there are multiple ways that crude oil components can adsorb to alter effective wetting, especially when an aqueous phase is also present.