The mechanisms of hypoxemia and of declining gas exchange in patients with treated and untreated pneumonia due to pneumocystis is not clear. Dr Hoffman has developed a microtechnique for the measurement of surfactant lipids from Bronchoalveolar Lavage Fluid. To date, 29 samples have been studied. There is evidence of surfactant lipid breakdown with an increase in lysophosphatidyl choline. There is also evidence of increased Phospholipase A2 activity in the lavage Fluid of these patients. The importance of these studies is that these observations may allow for the development of new or different therapies in this patient population. A manuscript is in preparation. This study has been extended to evaluate the effect of corticosteroid administration on surfactant lipid levels in the BAL of HIV infected patients with Pneumocystis pneumonia.