Relaxation of excited states and reactivity of ketoprofen (KP), one of the most popular nonsteroidal anti-inflammatory drugs, with indole and methylindoles have been studied with transient absorption and quantum chemical calculations. KP in the excited triplet state, (KP)-K-3*, abstracted a hydrogen atom from indole and methylindoles to afford a ketyl radical and a counter radical. The bimolecular quenching rate constants of (KP)-K-3* by indole and methylindoles, k(q), and the hydrogen atom abstraction rate constants, k(r), were obtained. The k(r) values for methylindoles were larger than that for indole; in addition, transient spectra at around 350 nm, assigned to the corresponding C-centered radical, was observed. These results indicate that (KP)-K-3* abstracts a hydrogen atom of the methyl group as well as that of N-H in the indole frame. These findings give us information on the reactivity of excited KP in the vicinity of tryptophan in a KP-protein complex, which will ultimately cause photosensitization on human skin.