Reaction byproducts from degradation of aqueous phenol by contact of gas d.c. corona discharge with treated water were analyzed by liquid chromatography. According to the retention time, three byproducts, pyrocatechol, hydroquinone, 1,4-benzoquinone, were identified. Also, acetic acid was detected as a final relatively stable byproduct by gas chromatography. A simple reaction model in which relevant elementary reactions are assumed to be first order was proposed to correlate the practical behavior of degradation processes.