This sixth article in the Performance Technologist's Toolbox series focuses on the critical incident method of data collection. Critical incidents are narrative descriptions of important events that occur on the job and how employees behave in those situations. Critical incidents document the work context, the specific situation that arose, the persons who were involved, what each person did and said, and the results. The incidents may be confined to a particular topic or may cover the breadth of work experience. Critical incidents provide a rich, personal perspective of life in an organization that facilitates understanding of the issues and obstacles people face and illuminates potential avenues for improvement. This article describes several methods used to collect information about critical incidents in an organization. These include focus groups, individual interviews, surveys, performance records, and work diaries. It also discusses the applications of critical incidents in several areas of performance technology and provides examples of those applications in organizations. The advantages and disadvantages of critical incidents as a data collection method are outlined, and guidelines for their use are provided.