Niemann-Pick disease (NPD) is a rare, inherited, autosomal recessive, lipid storage disease. The pathognomonic intracellular accumulation of sphingomyelin results in the production and accumulation of 'foam cells'. Interstitial lung disease is a rare manifestation of NPD. We present the case of a 48-year-old white female with NPD involving the lungs, liver and spleen. The chest radiograph showed bilateral, predominantly basal reticulonodular infiltrates and serial pulmonary function tests over a period of years showed preserved expiratory airflow and a severely decreased diffusion capacity for carbon monoxide (DLCO). In view of her visceral involvement, lack of neurological symptoms and survival into adulthood, we believe our patient represents a case of type B NPD. In this type of NPD, aside from prominent hepatosplenomegaly and sexual immaturity, significant pulmonary infiltration with 'Pick cells' has been reported. To date, no therapeutic modality has been shown to alter the natural history of this disease, which results in progressive debilitation and death. This case is unique in that it provides the longest physiological follow-up in the literature, and provides data on the natural history of pulmonary involvement in NPD.