The proton-transfer reactions to solvent from electronically excited o-, m-, and p-(trifluoromethyl)phenols (TFOHs) in water have been investigated by picosecond time-resolved fluorescence measurements. The rate constants for the proton dissociation of o-, m-, and p-TFOH are obtained to be 2.2 x 10(9), 8.6 x 10(8), and 2.5 x 10(8) s(-1), respectively. On the basis of the rate constants, the effects of substituent and deuterium isotope effects on the proton-transfer reactions are revealed.