Ab initio calculations are used to investigate the structure and stability of FOOCl. Infrared and UV spectroscopic properties are provided in order to facilitate its identification. The heat of formation of FOOCl is determined as 36.8 +/- 2 kcal mol(-1) using an isodesmic reaction scheme and is consistent with that estimated from bond additivity calculations. Using the computed heat of formation, the stability of FOOCl with respect to the FO + ClO, FOO + Cl, and ClOO + F dissociation limits is examined. The potential role of FOOCl in stratospheric chemistry is discussed.