Hard capsules containing 150 mg dipyridamole and 100 mg aspirin containing pellets were compared in 12 humans against the equivalent dose of conventional products given twice daily. The new product gave extended and more uniform levels of dipyridamole in the steady-state, with a lower incidence of undesirable side-effects, whereas aspirin levels were similar. The new product also had acceptable long-term stability provided it was stored under cool conditions and low humidity.