Pulmonary alveolar microlithiasis is characterized by the presence in pulmonary alveolus of round shaped little bodies containing concentric calcareous lamellas. The incidence is similar in all continents, in both sexes and it is higher in age brackets between 20 and 50 years. The disease is prevalent among family units. Clinical reports may suggest the hypothesis that the disease may be hereditary. Pathogenetic hypotheses may indicate that a reduced lung mucociliary function leading to an excess of alveolar mucus may induce the formation of alveolar microliths by mucus condensation. Microliths may appear either confined in particular areas of the lung or widespread. Chemically, microliths consist of large amounts of calcium and phosphorus and, in reference to histology, they consist of calcareous concentric lamellas which are placed around an amorphous or granular central nucleus. The dissociation between definite X-ray pattern of lungs and relative poor clinical symptoms is the most common characteristics of the disease. However, a certain degree of dyspnea with a productive cough may occur together with a sporadic hemoptysis and thoracic pains. X-ray pattern of the lung reveals dissemination of radio-opaque nodules which may make lungs appear to be sprinkled with sand. The evolutive course of the disease leads to pulmonary insufficiency which is related to the increase of number of microliths in several areas of lungs. The inability to identify clear etiological and pathogenetic elements makes difficult therapeutic approach which is palliative such as the use of diphosphonate, steroids and therapeutic BAL.