The pulmonary eosinophilias are a diverse group of disorders characterised by pulmonary infiltrates, rich in eosinophils usually associated with a peripheral blood eosinophilia. Known causes of pulmonary eosinophilia include fungi--in particular Aspergillus fumigatus, parasites, toxins and drugs. Pulmonary eosinophilias of unknown cause include Löffler's syndrome, acute and chronic eosinophilic pneumonia, the hypereosinophilic syndrome, bronchocentric granulomatosis and pulmonary eosinophilia associated with vasculitis. The chest radiographic appearances of pulmonary eosinophilia are often characteristic and HRCT in selected cases can give important additional information.