BACKGROUND During a decade of evaluating the clinical performances of anesthesiology residents at several hospitals, a consistently low frequency of faculty members' comments regarding residents' unprofessional behavior was observed. METHODS To identify the population of residents who behave unprofessionally and the predictive categories and performance patterns associated with unprofessional behavior, an examination was undertaken of 24 months of clinical performance records regarding the behaviors of 71 residents for 15 negative categories and overall performance. The residents were in training from 1982-83 through 1989-90 at the University Hospitals of Cleveland. The performance records consisted of narrative comments from faculty that were converted into z-scores. These performance scores were evaluated by using percentage distributions, stepwise regression, and neural networks. RESULTS Of the 71 residents, 15 (21%) received comments about unprofessional behavior, for a total of 27 comments (1% of all negative comments). Primarily, the residents' unprofessional behaviors involved unacceptable behavior (33%), abdication of responsibility (38%), and frank fabrications (15%). The 15 residents experienced significant problems in the areas of eagerness to learn, conscientiousness, composure, critical incidents, efficiency/organization, taking instruction, and knowledge. Problems with unprofessional behavior were not found for the 21 residents whose scores for overall performance were excellent. CONCLUSIONS The results expose a pattern of performance associated with unprofessional behavior, and suggest that clinical excellence and unprofessional behavior rarely coexist.