Disruptive and unprofessional behavior results in a poor culture of safety and may contribute to adverse events. This literature review sought to examine the incidence and types of unprofessional behaviors among medical students and residents. Although many studies show that trainees commit professionalism violations fairly regularly—for example, multiple studies show that up to 50% of residents falsify their duty hours—there was no clear evidence of an increase over time. The authors acknowledge that study of this area is impaired by lack of a standard definition and measurement strategy for unprofessional behavior and by a poor understanding of the relationship between professionalism violations and patient safety.