We report the direct measurement of the photolysis rate coefficient of ethyl nitrate to NO2 and the ethoxy radical: CH3CH2ONO2+h&ngr;→CH3CH2O+NO2 using a luminol chemiluminescence NO2 detector. The photolysis of ethyl nitrate is slow: at a temperature of 288 K and a zenith angle of 60¿, j1=0.45¿10-6 s-1. At a zenith angle of 0¿, j1 is estimated to be ca. 1.1¿10-6 s-1. This implies a photolytic lifetime of about one month in the planetary boundry layer. The photolysis frequency is very temperature dependent, and approximately doubles between 279 and 299 K. Observed photolysis rate coefficients agree, with experimental uncertainty, with coefficients calculated using recently measured absorption cross-sections and an assumed quantum yield of unity. ¿ American Geophysical Union 1988