This paper aims to identify success factors and remaining challenges relevant to the practice of process mining in the rail industry. Process mining is a method for analyzing processes based on event logs. In a case study, we examine three process mining projects performed at the largest rail organization in The Netherlands. Experiences gained in these projects are compared to success factors specified in literature. The projects were analyzed using observations, secondary data collection and semi-structured interviews. We were able to identify all success factors specified in literature in the case study. In addition, several new success factors are identified. These concern challenges regarding the implementation of process mining software, intra-organizational knowledge sharing and continuous availability of event logs. For the additional success factors identified, it was not yet possible to determine if they are industry specific or generic in nature.