Three thousand four hundred and ten patients recruited at 254 pharmacies took part in a national postal survey of the effect of prescription information leaflets. The patients had been prescribed penicillins, non-steroidal anti-inflammatory drugs (NSAIDs) or beta-adrenoceptor antagonists. The 1809 patients who received leaflets knew more about their medicines, especially the side effects and were significantly more satisfied than the 1601 patients who were not given additional written information. The leaflets were found to be effective when issued in the north, in the south and in small, medium and large towns. Patients of both sexes, all age groups and social classes were found to benefit from the leaflets and almost everyone (97%) thought they were a good idea. These results confirm and extend our previous findings and add further support for the routine use of information leaflets with prescribed medicines.