A procedure for preparing thin films of airblown asphalts and a spectroscopic study of such films throughout the infrared region of 2.5 to 15 microns are described. The relationship of transmittance of several absorption bands with the durability of the asphalt is discussed. Exposure to ultraviolet radiation produced changes in transmittance at four wavelengths which, in a series of asphalts studied, showed statistically significant correlations with durability.