Although mobile technologies are increasingly utilized for business purposes, many companies have found it difficult to successfully implement them. Not only do the rapid technological changes increase the risks of companies' investments into mobile technologies; many such applications have also failed to gain user acceptance. In contrast to the consumer domain, there are very few empirical studies of mobile applications' effectiveness from the perspectives of professional end-users. Furthermore, designing mobile business applications has become an increasingly iterative and incremental activity, and ex post evaluations by actual users can provide crucial feedback to an iterative design process. In this study, we seek to contribute to establishing a design cycle that closely links the building and the evaluation of mobile business applications. Our objectives are to (1) gain a better understanding of mobile business applications' success by means of ex post evaluations from end-users, and to (2) leverage these empirical insights to inform the design of mobile business applications. We carried out the study in collaboration with DEKRA Automotive, which offers expert services in the automotive sector with experience in mobile business applications. Our primary contribution is a systematic approach to using ex post evaluation as input for the iterative design of mobile business applications. We suggest an adapted version of the D&M IS Success Model, which has process quality as additional construct, as a basis for ex post evaluations of a mobile business application by its end-users. Furthermore, we illustrate how a performance-based analysis of the empirical results enables one to derive priorities and recommendations for future design iterations. Our results reveal that system quality and process quality are the main determinants of individual benefits of using mobile business applications. Our findings thus contradict other studies that identify information quality as a significant motivator of (consumer-oriented) mobile data services. We conclude that a mobile business application's design should focus on process quality, emphasizing functional support for operational tasks in a specific work context while ensuring system quality, which is largely affected by technology platform choices.