In the migration of object-oriented systems towards the aspect technology, after locating fragments of code presenting a crosscutting behavior and before extracting such code to aspects, transformations may be needed in the base program. Such transformations aim to associate crosscutting code to points of the base program that can be captured using the pointcut descriptor model of aspect-oriented languages. In this paper, we present a catalog of object-oriented transformations and demonstrate the importance of such transformations by reporting on a case study involving four systems that have been aspectized using AspectJ.