This document is the result of a conference on Biological Monitoring of Metals held in Rochester, June 2-6, 1986, organized jointly by the Environmental Health Sciences Center of the School of Medicine and Dentistry of the University of Rochester, NY, and the Scientific Committee on the Toxicology of Metals within the International Commission on Occupational Health (ICOH) at the Karolinska Institute and the National (Swedish) Institute of Environmental Medicine and the University of Umea, Sweden. The aim of the Conference was to define and evaluate the scientific basis for the biological monitoring of metals. The conference was co-sponsored by the World Health Organization through its International Program on Chemical Safety and received substantial encouragement and support from the Swedish Work Environmental Fund and the United States Environmental Protection Agency. This was the second conference organized jointly by the Scientific Committee on the Toxicology of Metals and The Toxicology Division of the University of Rochester. The previous joint conference was held in 1982 on the Reproductive and Developmental Toxicity of Metals. In addition, conferences have been organized by each group (see Appendices A and B). Several of these conferences are specially relevant to the topic of the current conference. These include the joint conference mentioned above and the conferences on dose-effect and dose-response relationship held in Tokyo in 1974 and on accumulation of metals held in Buenos Aires in 1972.