In recent years, many new over-the-counter (OTC) medications have resulted from the granting of OTC status by the U.S. Food and Drug Administration to drug entities that previously were available only by prescription (Rx). While the benefits to consumers of Rx-to-OTC switches may be substantial, they also involve some degree of risk, as usage typically expands and physician supervision diminishes. This study explores the potential utility of techniques of decision analysis in evaluating the balance of these benefits and risks. Histamine H2 receptor antagonists (H2-blockers), which are currently available only by prescription, are presented as a case study and were examined to determine how OTC availability of these agents would alter the patterns, effectiveness, and risks of self-treatment for acid-peptic disorders. Currently, about 5.7 million persons experience an episode of dyspepsia during any given quarter, of whom 3.5 million self-medicate with antacids. Study results indicate that OTC availability of H2-blockers would: 1) increase the proportion of persons with dyspepsia who self-medicate from 61.8% currently to 64.1%; 2) increase the proportion of persons who experience complete relief of their symptoms while self-medicating from 37.9% currently to 43.2%; 3) result in 14 additional cases of serious hematologic disorders and an additional 22,000 instances of minor side effects per quarter, but cause the overall rate of side effects among persons who self-medicate to decline; 4) cause an additional 300 persons per quarter with gastric cancer to self-medicate before seeking professional care, but cause no change in the median time between onset of symptoms and the decision to seek such care; and 5) decrease by 277,000 the number of persons per quarter who seek professional care for dyspepsia. On balance, results suggest that OTC H2-blockers may be a relatively safe and effective means of self-care for acid-peptic disorders, and may substantially reduce the number of patient encounters with the medical care system for minor gastrointestinal complaints. This study also illustrates the potential utility of the techniques of decision analysis to the formulation of drug regulatory policy.