In studies of the photoproduction of triplet excited benzophenone in cyclohexane by picosecond absorption spectroscopy (266-nm pump), it is shown that the presence of dissolved oxygen at 1 atm of pressure decreases the triplettriplet 347-nm transition by 50% in less than 25 ps, indicating the presence of a stable ground-state oxygen-benzophenone complex. This work suggests that there may be a need to reevaluate any triplet risetime and quantum yield experiments performed on aromatic/carbonyl compounds in nondeoxygenated solutions. 1986, American Chemical Society. All rights reserved.