Background: Agile software development has been increasingly adopted during the last two decades. Nonetheless, many studies show that using agile methods as defined in the literature does not work very well. Thus, companies adapt these methods by just using parts of them (called agile practices). Objective: The goal of the literature study was to understand which agile practices are used in industry under different circumstances, such as different project types, domains, or processes. Method: We conducted a mapping study of empirical studies using agile practices in industry. The search strategy identified 1110 studies, of which 24 studies including 68 projects were analyzed. Results: The results of this study show that there are practices that are used more often and that the domain and the process also influence the application of different practices. Additionally, the findings confirm the assumption of Ken Schwaber that in most cases, agile methods are not used "completely" but that rather certain practices are adopted. Conclusions: Our results can be used by researchers to get a better idea of where and how to follow up research as well as by practitioners to get a better idea of which practices fit their needs and which are used by others. Therefore, our contribution increases the body of knowledge in agile practices usage.