BACKGROUND AND AIMS: The Food and Drug Administration approval and subsequent launch of over-the-counter (OTC) omeprazole raises the question whether consumers would use OTC omeprazole appropriately in a "real world" setting. METHODS: A 3-month observational study was conducted in an OTC setting to determine whether consumers could (1) correctly self-select to use omeprazole for frequent heartburn, (2) comply with a product label that calls for 14 consecutive days of once-daily dosing, and (3) use more than 14 doses of medication only under the advice of a physician. Consumers were interviewed at 5 shopping malls in geographically distinct areas of the United States and asked whether they had heartburn. Of the 1999 self-reported heartburn sufferers, 866 determined the product was appropriate for their condition and purchased the product; of these, 758 (88%) returned diaries documenting product usage and physician contact. RESULTS: OTC consumers accurately self-selected; more than 90% of participants had heartburn 2 or more days/week. Analysis of diary data showed a high degree of compliance to label use directions; only 3% of subjects took more than 14 doses without consulting a physician. After 3 months, 43% of subjects did not have recurrence of heartburn. Overall, 75% of subjects had contact with a physician about heartburn before, during, or soon after the study (26% contacted a physician during the 3-month study). Of the 758 subjects, only 1 subject took more than 14 tablets without consulting a physician and had recurrence of heartburn. CONCLUSIONS: Actual use data support that consumers accurately self-select if an OTC proton pump inhibitor is appropriate for use, comply with a 14-day regimen in the OTC setting, and appropriately seek physician involvement for longer-term management of frequent heartburn.