A wide range of research on the toxic pulmonary effects of beryllium (7440417) was reviewed. Early toxicological studies on beryllium were contradictory; by 1950, however, the evidence was clear that beryllium was toxic and that occupational exposure represented a major health hazard. Different animal species were exposed to beryllium aerosols characterized with respect to concentration and particle size, and the phases of the response to exposure described. The acute disease in humans is marked by inflammation and edema of contacted tissue, conjunctivitis, nasopharyngitis, tracheobronchitis, dermatitis, and/or pneumonitis. Treatment includes bed rest, oxygen therapy, mechanical ventilation when needed, and corticosteroids. The chronic disease is systemic, granulomatous, and manifested primarily in the lungs; long term exposure is required and the latency period ranges from months to 25 years. Diagnosis based on clinical, radiographic, and lung function evidence has been found to be difficult. Epidemiological studies discussed included morbidity and mortality, as well as assessment of subclinical effects of beryllium. The mechanisms of disease were reviewed with respect to lung function, histopathology, and cellular responses (macrophage uptake and clearance; immune responses). A model of the cellular mechanisms of beryllium toxicity incorporating inflammatory and immune responses was developed. Future research priorities in epidemiology, toxicology, immunology, and disease prevention were discussed.