Growing recognition has been given to disability and death occurring in workers exposed to a variety of occupational hazards, and in the community as a consequence of environmental exposure. Moreover, there is constant accrual of new and unforeseen environmental hazards. Both industrial and rural occupations involve the use of many chemical, biological, and physical agents which may spill over into the general environment often with catastrophic results. The resultant spectrum of diseases ranges from pneumoconiosis caused by pulmonary mineral dust, to lung cancer and pleural mesothelioma related to asbestos, or liver angiosarcoma caused by vinyl chloride. These diseases may be prevented by appropriate industrial and hygienic measures or by interruption of the biological chain of events resulting in morbidity. The detection and investigation of occupational-environmental disease serves the cause of justice and permits due compensation, complements and validates environmental and occupational epidemiology, and is most likely to result in adoption of preventive measures. Medical-legal investigation comprise the following steps: 1) detection of cases (complete occupational history bearing in mind the delayed appearance of many of these diseases; clinical protocol and circumstances of death); 2) determination of pathological lesions (complete medical-legal autopsy and awareness of the potential pertinent pathological lesions and of the pathological markers present in some occupational diseases); and 3) detection, characterization, and quantitation of the causative agent (microscopy, ultramicroscopy, minerology, physical and chemical methods). Forensic detection and investigation of environmental-occupational disease may provide data otherwise not readily available.