Information on adverse drug effects is collected to monitor patterns of use, detect new safety signals that were not discovered in clinical trials, and update benefit:risk profile of marketed drugs. Accurate information on the safety profile and the limitations of use is in the best interest of patients and physicians as well as 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 event. The main limitations are the lack of epidemiological indicators, variable quality of data, and lacking causality assessments. The system needs to improve to achieve higher accuracy and speed of detection of safety data to provide valid, reliable, and accurate information for benefit:risk assessment.