Proprietary antacids represent a multimillion dollar business in this country. Marketing surveys have shown that approximately one-half of American adults have used antacids. Twenty-seven percent of adults take 2 or more doses per month. Seventy-five percent of total antacid consumption is by heavy users, defined as greater than 6 doses per week (less than 5% of adults). We investigated why apparently healthy people are heavy antacid users. Thirty-seven heavy users were evaluated. The median duration of antacid use was 20 years, and most took antacids 2-6 times per day, concentrated through the work week. The primary diagnosis was reflux esophagitis in 31 (84%), peptic ulcer disease in one, and nonulcer dyspepsia in five. Ninety-five percent had symptoms consistent with reflux esophagitis. Thirty-three completed a 1 month double-blind, randomized cross-over trial of antacid tablets (14 mEq neutralizing capacity per tablet) versus placebo. Twenty-nine correctly identified the antacid product (p less than 0.0001). Twenty-three subjects underwent Bernstein tests and endoscopy; 21 had positive Bernstein tests, 13 had definite esophagitis as determined endoscopically. We conclude 1) heavy proprietary antacid tablet use in the adult male is not an expression of functional disease but is due to reflux esophagitis, 2) tablet use can be effective symptomatic treatment, and 3) history is an adequate evaluation for most heavy antacid tablet users.