Reaction of one-electron oxidant (Br2^•-) with tryptophol (TP) and 5-hydroxytryptophol (HTP) have been studied in aqueous solution in the pH range from 3 to 10, employing nanosecond pulse radiolysis technique and the transients detected by kinetic spectrophotometry. One-electron oxidation of TP has produced an indolylradical that absorbs in the 300-600 nm region with radical pKa= 4.9±0.2, while the reaction with HTP has produced an indoloxyl radical with λmax at 420 nm and radical pKa <3. Hydroxyl radicals (^•OH) reactwith these two compounds producing ^•OH radical adducts that undergo water elimination to give one-electron-oxidized indolyl and indoloxyl radical species, respectively. The indoloxyl radicals react with the parent compound to form dimer radicals with an average association constant of (6.7±0.4) 10⁴ M^-1. No such dimerization is observed with indolyl radical, indicating that the presence of the 5-hydroxy group markedly alters its ability to form a dimer. A possible explanation behind such a difference in reactivity has been supported with ab initio quantum chemical calculations.