BACKGROUND Better understanding of medical students' perceptions, attitudes, and knowledge about antimicrobial prescribing practices could facilitate more effective education of these future prescribers. METHODS A 24-item electronic survey on antimicrobial prescribing and education was administered to fourth-year medical students at the University of Miami, the Johns Hopkins University, and the University of Washington (January-March 2012). RESULTS Three hundred seventeen of 519 (61%) students completed the survey; 92% of respondents agreed that strong knowledge of antimicrobials is important in their careers, and 90% said that they would like more education on appropriate use of antimicrobials. Mean correct knowledge score (11 items) was 51%, with statistically significant differences between study sites and sources of information used to learn about antimicrobials. Only 15% had completed a clinical infectious diseases rotation during medical school; those who had done so rated the quality of their antimicrobial education significantly higher compared to those who had not (mean, 3.93 vs 3.44, on a 5-point scale; P = .0003). There were no statistically significant associations between knowledge scores and having had an infectious diseases clinical elective. Only one-third of respondents perceived their preparedness to be adequate in some fundamental principles of antimicrobial use. CONCLUSIONS Differences exist between medical schools in educational resources used, perceived preparedness, and knowledge about antimicrobial use. Variability in formative education could frame behaviors and prescribing practices in future patient care. To help address the growing problem of antimicrobial resistance, efforts should be undertaken to ensure that our future doctors are well educated in the principles and practices of appropriate use of antibiotics and antimicrobial stewardship.