The purpose of this paper is to provide the reader with an overview of the biomedical and epidemiological characteristics of asbestos-related disease based upon currently available information. Epidemiological and experimental data developed over the past 20 years have greatly added to our knowledge of the biological effects of asbestos, particularly in relation to clinical disease. This information has substantially strengthened the evidence linking asbestos to specific health effects. Lung cancer and mesothelioma are clearly the most important asbestos-related causes of death among exposed individuals, although the accumulated data is suggestive of the existence of an excess risk of gastrointestinal and a variety of other neoplasms. Animal studies confirm the human epidemiological results and indicate that all commercially available fiber types are capable of producing lung cancer and mesothelioma. Experimental implantation and injection studies also show that the carcinogenicity of mineral fibers (including asbestos) is directly related to their dimensionality and not their chemical composition. Although the asbestos-related medical and scientific literature is voluminous, many issues related to the biological activity of asbestos fibers are as yet unresolved. Due to experimental and analytical limitations, questions concerning risk at low-level exposure, dose-response relationships, and individual susceptibility remain problematic.