A case report of a diffuse alveolar lipoid pneumonia occurring in a patient incapable of giving a proper history underlines the diagnostic difficulty of lipoid pneumonias. Till now, unless the diagnosis was made at necropsy, one relied on a history of prolonged consumption of medications containing mineral oil, with evidence on open lung biopsy of excess fatty material in the pulmonary parenchyma. Chromatography on thin slices of the lipid extract of bronchiolo-alveolar lavage liquid fixed in silica gel, a simple technique, should rapidly give the diagnosis. In the alveolar form of the disease bronchopulmonary lavage returns a significant quantity of paraffin oil and may be considered as a therapeutic method.