A study was designed to determine the acid neutralization capacities (ANCs) of the new Canadian antacid formulations and to compare these products with standard antacid products in terms of lot-to-lot consistency, ANC, sodium and "calorie" contents, and price to the pharmacist. Twenty-three liquid and 18 tablet antacids were tested. The concentrated liquid antacids (Mylanta-2 Extra Strength, Amphojel 500, Gelusil Extra Strength, Maalox TC and Diovol Ex) were found to have the highest ANCs. Six of the tablet antacids (Amphojel, Amphojel Plus, Camalox, Gelusil-400, Maalox and Mylanta-2) were found to have greater ANCs than 15 of the liquid antacids. Between-lot variation exceeded that of within-lot variation in 10 of the 14 liquid antacids for which this variation could be tested. The concentrated liquid antacids provide the highest ANCs with the lowest dosage volume and sodium and calorie contents. Some tablet antacids have the potential to be used as alternatives to liquid antacids because of their high ANC and patient convenience. The inclusion of ANC on the labels of antacid products would assist in the rational determination of the dose of these products.