Pharmacovigilance information collected through post-authorization surveillance systems is used to change drug labeling and update benefit:risk profile of marketed drugs. Physicians make clinical decisions based on this information. Accurate assessment is in the interest of all stakeholders in the system, from patients and physicians to manufacturers and insurers. Denial of a useful drug to a patient who may benefit from it is as harmful as prescribing it to a patient who is likely to develop an adverse effect. The system should, therefore, strive for greater accuracy and speed of detection of safety data in order to provide valid, reliable and accurate information for benefit:risk assessment.