The clinical efficacy of a combined immediate-release and sustained-release preparation of isosorbide-5-mononitrate for angina pectoris is observed within a few minutes of administration. The preparation reduces the number of silent and painful ischaemic episodes and increases work and exercise capacity. The pharmacokinetic profiles accord with the circadian variation in cardiovascular disease. Drug levels fall significantly at night and tolerance to the haemodynamic and antianginal effects is not seen. Once-daily administration is appreciated by patients. The preparation also shows promise in treating heart failure.