This study was set up to document the variability of prescribing information from different sources concerning indications, side effects and cautions of selected drugs. An original method to measure the degree of information agreement among different written materials, such as summaries of product characteristics, package inserts and data sheets, and a widely accepted reference text was developed. The results show that there is substantial disagreement in the materials available to prescribers and patients in different countries. Disagreement was even found within a single country when written materials from different brands of the same drug were compared. The discordance can be explained by the fact that the evidence available for each drug is considered/assessed differently by separate countries. It is argued that the discrepancies found may mislead prescribers, patients and those comparing drug-use patterns across countries. National regulatory authorities have a key role to play in remedying this situation, and a two-pronged approach is proposed. At the international level, national authorities should strengthen collaboration and information interchange and, at the national level, should implement appropriate measures aimed at removing contradictory statements on drug-information materials that have no reason to be different. Finally, further training and continued education aimed at drug regulatory officials could provide the necessary knowledge and enable national authorities to meet the need for drug information that is independent of commercial interests.