It is important that data on adverse reactions are collected and the risks of adverse effects in different patient groups are assessed. The results of studies need to be analysed, allowing the incidence and potential costs of adverse drug reactions (ADRs) to be estimated and the risks and benefits of different treatments to be compared. In addition, the findings of these studies and analyses need to be communicated appropriately. These issues were discussed at a session of the 7th Conference of the European Society of Pharmacovigilance [Ankara, Turkey; September 1999].