We investigate the relationship between reverse engineering and program comprehension on the one hand, and software process on the other. To understand this relationship, we select one particular existing software process, extreme programming (XP), and study the role played in it by program comprehension and reverse engineering. To that end, we analyze five key XP practices in depth: pair programming, unit testing, refactoring, evolutionary design, and collaborative planning. The contributions of this paper are (1) the identification of promising research areas in the field of program comprehension; (2) the identification of new application perspectives for reverse engineering technology; (3) a critical analysis of XP resulting in research questions that could help resolve some of the uncertainties surrounding XP; (4) a process assessment framework for analyzing software processes from the comprehension and reverse engineering point of view.