The national spontaneous adverse event (AE) monitoring system administered by the Health Sciences Authority (HSA) is supported by a network of healthcare professionals, who actively report adverse reactions of health products observed in clinical practice. When a new health product is submitted for registration, the demonstration of its efficacy and the evaluation of its safety are generally based on a limited number of patients in clinical trials. In addition, the exclusion of certain patient groups in clinical trials, the lack of significant long-term treatment experience, and limitation of concomitant therapies do not allow a thorough evaluation of the safety profile. Under such circumstances, the detection or confirmation of rare AEs is particularly difficult during the pre-registration development of the product. In order to develop a comprehensive picture of clinical safety, marketed health products have to be closely monitored for their safety when used in actual practice.Surveillance of health products is an important aspect of the continual benefit-risk assessment of the product. Surveillance activities include mandatory reporting from pharmaceutical manufacturers, spontaneous reporting from health professionals, literature reviews and the exchange of regulatory information with other national drug regulatory bodies. Among these approaches, the spontaneous AE reporting by the health professionals forms the cornerstone of post-marketing safety surveillance. It remains one of the most important ways of monitoring the safety of a health product throughout its marketed life.When an AE occurs, the assessment of the possible contributory roles of a health product is an important part of the clinical diagnostic process. This is valuable information that many physicians have shared with HSA over the past years, which has enabled us to identify key safety signals from the local use of marketed health products.