PURPOSE: To assess medical students' and residents' experiences with defensive medicine, which is any deviation from sound medical practice due to a perceived threat of liability through either assurance or avoidance behaviors. Assurance behaviors include providing additional services of minimal clinical value. Avoidance behaviors include withholding services that are, or avoiding patients who are, perceived as high risk. METHOD: The authors conducted a cross-sectional survey of fourth-year medical students and third-year residents in 2010. Respondents rated how often malpractice liability concerns caused their teams to engage in four types of assurance and two types of avoidance behaviors using a four-point scale (never, rarely, sometimes, often). Respondents also rated how often their attending physicians explicitly recommended that liability concerns be taken into account when making clinical decisions. RESULTS: Overall, 126 of 194 medical students (65%) and 76 of 141 residents (54%) completed the survey. Of the responding medical students, 116 (92%) reported sometimes or often encountering at least one assurance practice, and 43 (34%) reported encountering at least one avoidance practice. Of the responding residents, 73 (96%) reported encountering at least one assurance practice, and 33 (43%) reported encountering at least one avoidance practice. Overall, 50 of 121 medical students (41%) and 36 of 68 residents (53%) reported that their attending physicians sometimes or often explicitly taught them to take liability into account when making clinical decisions. CONCLUSIONS: Medical trainees reported frequently encountering defensive medicine practices and often being taught to take malpractice liability into consideration during clinical decision making.