BACKGROUND AND OBJECTIVES: Few national data exist on physicians' use of and beliefs about placebos in routine health care. METHODS: We mailed a 22-question, confidential survey about placebo use and beliefs to a random sample of 1,000 members of the American Academy of Family Physicians. RESULTS: A total of 412 of 970 (43%) eligible physicians responded, and 56% of respondents said they had used a placebo in clinical practice. Forty percent of respondents had used an antibiotic as a placebo, and 11% had used inert substances. The most common reason for prescribing placebos was "after unjustified demand for medication." Eighty-five percent of respondents believed placebos can have both psychological and physical benefits. The majority (61%) recommended a placebo over offering no treatment, while 8% said clinical placebo use should be categorically prohibited. Nearly all respondents believed a number of routine clinical practices promote the placebo effect. CONCLUSIONS: Many US family physicians use placebos and generally believe the placebo effect has both psychological and physical benefits. Physicians recognize the broader application of the placebo effect but they commonly use active medication as placebos. The responses to this survey raise important questions about the appropriate use of placebos and the therapeutic value of the placebo effect in clinical practice.