We provide a resolution-based proof procedure for modal and description logics that improves on previous proposals in a number of important ways. First, it avoids translations into large undecidable logics, and works directly on modal or description logic formulas instead. Second, by using labeled formulas it avoids the complexities of earlier propositional resolution-based methods for modal logic. Third, it provides a method for manipulating so-called assertional information in the description logic setting. And fourth, we believe that it combines ideas from the method of prefixes used in tableaux and resolution in such a way that some of the heuristics and optimizations devised in either field are applicable.