A diphosphonate, disodium etidronate, a compound known to inhibit microcrystal growth of hydroxyapatite was given to a 3.5-year-old girl with pulmonary alveolar microlithiasis (PAM) that was symptomatic. The drug was used for approximately 36 months in a single daily dose of 15 mg/kg. No significant side effects were encountered with somewhat clearing of lung bases in chest radiograms and subjective improvement in general condition. These findings suggest a role of diphosphonates in the treatment of PAM.