The most common sources for lipids producing radiographic or clinical evidence of disease in the lungs are endogenous lipids and inhaled (exogenous) mineral oil. Endogenous lipoid pneumonia arises when lung tissue breaks down distal to an obstructed airway leading to the release of cholesterol and other lipids, producing airspace disease. Exogenous lipoid pneumonia occurs most frequently in the elderly following habitual mineral oil use. Many patients have no specific predisposing cause for aspiration of the ingested mineral oils. Symptoms, found in only half of the patients reviewed, include chronic cough and sputum production. Radiographically, the lesions are usually ill-defined radiopacities that mimic carcinoma of the lung. The inhaled mineral oil incites a foreign-body reaction, producing a granuloma with multinucleated foreign-body giant cells and fibrosis surrounding lipid droplets. Diagnostic strategies such as sputum examination for lipids and transthoracic needle aspiration are discussed. These procedures may help to avoid thoracotomy in elderly, often debilitated patients with lipoid pneumonia.