The intent of this article is to provide an overview of surveillance systems dealing with pesticide intoxications. Surveillance, medical monitoring, and the components of a surveillance system are discussed. Information is presented on how to make a diagnosis of environmental or occupational pesticide intoxication, examples of different case definitions, and the steps in investigating a pesticide disease outbreak. Examples from various countries are used to illustrate acute pesticide intoxication surveillance, pesticide exposure surveillance, and medical monitoring of pesticide-exposed workers. Finally, a list of informational sources for pesticide toxicology, medical diagnosis and treatment, and surveillance data is provided. It is anticipated that this information will assist those individuals or organizations seeking to develop such a system, evaluate an existing system, or gain a better understanding of data derived from such systems.