We wish to report a new method for following the rates of autoxidation reactions, and the use of the method in a study of the autoxidation of styrene. The method involves monitoring the decrease in the ultraviolet absorption band which results from the interaction of oxygen with most organic solvents. This absorption band was discovered by Evans4in 1953. It rapidly appears when oxygen is bubbled through an organic solvent in a UV cell, and it just as rapidly disappears when the solution is purged with nitrogen. Evans at first4aattributed the band to a contact charge transfer complex5between oxygen and the organic solvent. He later suggested4that this band is due to a singlet-to-triplet absorption by the organic material which is enhanced by the presence of the paramagnetic oxygen molecule. This latter explanation is the one which is most commonly accepted today. 6 Table 1 lists the absorption maxima of the Evans peak for several common organic solvents. The only solvent which we have yet discovered which does not have an Evans peak is CC14.