Application Domain Knowledge and Programmers’ Mental Representations ABSTRACT Despite the fact that the application domain is regarded as critical to software development, previous research investigating software development has focused on the implementation domain or computing element. To investigate the role of application knowledge in computer program comprehension and enhancement, 24 information systems professionals studied and enhanced computer programs from two different application domains: one familiar, one unfamiliar. In a familiar application domain, programmers developed a more accurate mental representation of a computer program across four different knowledge categories. Hence, it appears that application domain familiarity helps programmers develop all aspects of their mental representation, rather than just certain types of knowledge. The results of this study demonstrate that application domain knowledge is an important element in programmers' ability to comprehend computer programs.