According to market surveys, antacid use is common in the general population. This study of antacid use in a university-based family-practice clinic supports this conclusion. In a sample of 731 adult patients, 51.3% reported taking antacids at least once in the previous six months and 10.9% took antacids daily. Highest antacid users were people 31-40 years of age. Heartburn was the most common symptom in patients taking antacids, but antacid use increased as the patients reported more symptoms. Antacid use by patients is often unknown to the physician. This has some clinical importance because antacids are known to interfere with the absorption of some commonly used drugs. Physicians should routinely ask their patients about antacid use, as well as about their use of other over-the-counter products.