Public concern is increasing over the safety of medicines, particularly serious adverse events detected after extensive use of products in the general marketplace. This concern has led to the need for prompt evaluation of safety signals within large populations following drug approval. The most relevant and available data resources primarily include electronic health care claims and electronic medical records and can be used to identify new safety issues and to evaluate known or suspected signals. In this review paper, we (1) summarize the data resources available for detection and evaluation of safety signals and (2) critically describe these resources and methods used in drug safety research. For each type of data resource, we summarize the characteristics and describe the associated applications and appropriate methods. To place each data resource and method in perspective, we provide examples from disease areas with substantial public health impact. We conclude that in certain circumstances these data resources can be valuable for the relatively cost-effective evaluation of serious adverse events in users of specific medications. However, implementation of such research requires a thorough understanding of the strengths and weaknesses of the data sources and the pharmacoepidemiologic methods used for analysis.