Initial studies in this new project involve establishing a standard protocol for chemical treatment of pregnant rats with CdS02. These studies include determining which gestation days to treat and the appropriate dose in order to obtain an optimal effect on the fetal and neonatal respiratory tract. A prototype nose-only plethysmograph was constructed for measuring pulmonary function in neonatal rats during inhalation challenge to irritant gases. Initial testing and evaluation of this system is in progress. Methods for evaluating histological and biochemical endpoints are also being developed.