The fate of total lipids, proteins and carbohydrates in the trachea, lungs, and heart of the common ground squirrel, Funambulus pennanti, have been determined after separate exposure to three principal air pollutants, carbon monoxide (CO), sulphur dioxide (SO2), and nitrogen dioxide (NO2). Exposure to all of these gases produced edematous conditions; however, the moisture content of heart muscle was reduced. Carbon monoxide (CO) and NO2 are more toxic to pulmonary lipids than SO2. The lipid of the heart decreased, least effects noted with SO2 treatment. Mechanical properties of the lungs were changed by alteration of the lung lipids causing changes in the surface tension. Changes in protein content were caused by altered membrane permeability. Comparative data on the carbohydrates indicated adverse effects by the pollutants.