Action research (AR) is based on a collaborative problem-solving relationship between researcher and client, and the aims of this research are to solve the problem and to generate new knowledge. The chapter describes and shows how several different methods might be used for data collection in an AR-based study. Concepts related to AR are described; in addition, the multifaceted role of the action researcher is described, along with a set of data quality criteria for evaluating the quality of an AR-based study. Then follows a thorough description of a Danish AR-based pharmacy practice study. The chapter concludes with a list of experience-based recommendations for others who are interested in running an AR-based study. This is followed by an Appendix describing four different AR-based studies.