Purpose: To determine public perceptions of the effect of direct-to-consumer advertising (DTCA) of prescription medications on health behaviors, health care utilization, the doctor-patient relationship, and the association between socioeconomic status and these effects.Methods: Cross-sectional survey of randomly selected, nationally representative sample of the US public using computer-assisted telephone interviewing. Main outcome measures: numbers and proportions of respondents in the past 12 months who, as a result of DTCA, requested preventive care or scheduled a physician visit; were diagnosed with condition mentioned in advertisement; disclosed health concerns to a doctor; felt enhanced confidence or sense of control; perceived an effect on the doctor-patient relationship; requested a test, medication change, or specialist referral; or manifested serious dissatisfaction after a visit to a doctor.Results: As a result of DTCA, 14% of respondents disclosed health concerns to a physician, 6% requested preventive care, 5% felt more in control during a physician visit; 5% made requests for a test, medication change, or specialist referral, and 3% received the requested intervention. One percent of patients reported negative outcomes, including worsened treatment, serious dissatisfaction with the visit, or that the physician acted challenged. Effects of DTCA were greater for respondents with low socioeconomic status.Conclusions: DTCA has positive and negative effects on health behaviors, health service utilization, and the doctor-patient relationship that are greatest on people of low socioeconomic status. The benefits of DTCA in terms of encouraging hard-to-reach sections of the population to seek preventive care must be balanced against increased health care costs caused by clinically inappropriate requests generated by DTCA. (J Am Board Fam Pract 2004;17:6 -18.)