The research reported in this article provides descriptions of design activities and of the evolving designs for expert procedural and expert object-oriented (OO) designers and for novice OO designers who also had extensive procedural experience. Ten experienced programmers were observed while designing software that would serve as a scoring system for swim meet competitions. Talk-aloud protocols were collected and analyzed for different types of cognitive activities and strategies that occurred during the course of design. In particular, we analyzed both the design activities and the level of abstraction of the designs over the course of time for each group in order to examine the role of several design strategies described in the literature as central in procedural design. In the course of these analyses, we developed a generic way (design template) of comparing the final designs of designers in different paradigms. Using this template, we analyzed the designs in terms of their completeness for different views at different levels of abstraction. Our analyses of procedural and OO designers-in terms of their cognitive activities, design strategies, and final designs-provide a detailed comparison between design paradigms in practice. A variety of descriptive results are discussed in terms of positive transfer, interference, and implications for design training. Findings are also discussed in terms of the relation between tasks and design paradigms.