Safety research in high-reliability industries, such as aviation, has clearly shown that the causes of accidents are primarily related to deficiencies in nontechnical (cognitive and social) skills, rather than a lack of technical expertise. Investigations into causes of error in anesthesia have revealed a similar pattern. The aviation industry uses behavioral marker systems to structure the training and assessment of pilot crew resource management (CRM) (nontechnical) skills. These are empirically derived taxonomies of the principal required nontechnical skills, and an observation-based rating system for assessing their component behaviors. In medicine, the enthusiasm for adopting CRM-type training needs to be underpinned by the development of a properly tested nontechnical skills framework for a given specialization. A research project involving industrial psychologists and consultant anesthetists, and funded by the National Health Service Education for Scotland, is developing and evaluating a behavioral marker system for anesthetists. It has produced and experimentally evaluated a taxonomy of anesthetists' nontechnical skills (ANTS), which can be used to guide professional syllabi, offer a method for evaluating performance, and improve the quality of feedback to trainees. This paper will provide an overview of the ANTS System and the results of usability trials conducted in the operating theatre.