Controlled clinical trials have provided some useful evidence of the effectiveness or lack of effectiveness of antacids and anticholinergic drugs. However, few such trials are free of serious methodologic or clinical criticism, and the use of these agents cannot be defined with any degree of scientific certainty. Their principal uses still focus on reduction of gastric acid content, and their best use requires individualization for each patient. With anticholinergic drugs there is little if any pharmacologic effect without some side-effects, and dose adjustment may be more important than the choice among the many drugs considered effective. Some new antacids offer better neutralization than old ones, but are at least as likely to affect colonic function. Although toxicity, side-effects, and interactions with other drugs are minimal, they should be watched for.