Pulmonary alveolar proteinosis is a rare disease characterized by the accumulation of lipoproteinaceous material derived from alveolar surfactant in the alveoli, with a consequent deterioration in gas exchange. Pathogenesis is related to impaired phagocytic function of alveolar macrophages. In recent years, a new treatment for pulmonary alveolar proteinosis-consisting of subcutaneous administration of granulocyte-macrophage colony-stimulating factor (GM-CSF)-has become available. The commonly accepted treatment, and the one to have shown greatest efficacy in pulmonary alveolar proteinosis, is whole lung lavage. Instead of subcutaneous administration, GM-CSF can also be inhaled as an aerosol. This route of administration of GM-CSF is safe and effective in the treatment of pulmonary alveolar proteinosis and represents an alternative to subcutaneous administration or whole lung lavage. We present a patient with pulmonary alveolar proteinosis who was treated with inhaled GM-CSF and describe her clinical and functional outcome after 1 year of treatment.