The reactivity and spectroscopic characteristics of the 1-azaxanthone triplet state in aqueous solutions indicate that inversion of states in the triplet manifold occurs in this solvent. Both the reactivity and spectroscopy of 1-azaxanthone suggest a predominantly pi,pi* character for the lowest triplet state in aqueous solutions, in contrast with organic solvents where 1-azaxanthone has n,pi* character, even in polar media. The pH-dependent properties of the 1-azaxanthone triplet and its ketyl radical were examined, Despite the high reactivity of 1-azaxanthone toward photoreduction in organic solvents, in micellar systems the generation of ketyl radicals is inefficient. Studies of magnetic field effects on radical-pair behavior reveal similar characteristics to those observed with other carbonyl compounds, where geminate reaction and micellar exit are competing processes.