This paper utilizes a many-country, many-product Ricardian trade model to evaluate the usefulness of measures of revealed comparative advantage (RCA) in academic and policy analyses. I find that, while commonly used indexes are generally not consistent with theoretical notions of comparative advantage, certain indexes can be usefully employed for certain tasks. I explore several common uses of RCA indexes and show that different indexes are appropriate when attempting to (a) evaluate the differential effect of changes in trade barriers across producers of different products, (b) identify countries who are relatively close competitors in a given market, or (c) recover patterns of relative productivity.