Animals have provided a surrogate for the study of human health. This has been particularly important in the definition of the effects of pollutants generated in our society. Electromagnetic fields provide an example of the use of animals as models. A review of the animal model literature provides the following information in response to three basic toxicologic elements in defining whether electromagnetic fields are a hazard: 1. Various scientific committees have determined that, in general, exposure to electromagnetic fields, individually or combined, causes a response in animals. Exposure facilities must be carefully constructed and characterized to ensure that artifacts or environmental factors are not actually the cause of the reported effects. 2. It would appear that various components of the nervous system, some circadian rhythms of the body and the pineal gland are responsive to electromagnetic field exposure. Data for other systems are either negative, contradictory or inconclusive. With the exception of the pineal gland, there is little reliable information on dose response, minimum duration required for the effect and whether the effect is reversible or permanent. 3. there are very little animal data available to reliably conclude that exposure represents a hazardous situation. There are questions of the significance of some of the animal data, such as changes in circadian rhythms or suppression of melatonin production. There are also concerns raised by human epidemiology data not addressed by the animal data base. The statistical community is being approached to consider two questions: (1) Can the large amount of negative data be utilized in a quantifiable risk assessment methodology to provide a reasonably reliable definition of risk? (2) Can data from similar studies be statistically combined resulting in larger experimental groups, reducing variability, and potentially clarifying trends or contradictory results?