The accelerated stability of diltiazem in aqueous sugar solutions, with or without sodium dihydrogen phosphate, was investigated using a high-pressure liquid chromatographic method. The degradation of diltiazem in all sugar solutions followed pseudo first-order kinetics. The shelf-life of diltiazem in the pure sugar solutions (0.28 M) was arranged in the following order: fructose greater than dextrose greater than sucrose = sorbitol = mannitol greater than lactose. Incorporation of 0.1 or 0.2 M sodium dihydrogen phosphate in the sugar solutions resulted in a decrease in the shelf-life of diltiazem. The reduction was most pronounced with fructose. The use of the above sugars (with the exception of lactose) would make it possible to prepare liquid dosage forms of diltiazem extemporaneously which will retain their potencies for a minimum of 50 days.