The second-order rate constant (k(2)) for the aqueous-phase reaction Cl-2(aq) + OH- --> HOCl + Cl- was determined by measuring the uptake of gas-phase chlorine into water in a bubble train flow reactor. In making these measurements, we avoided some of the difficulties encountered in earlier studies. Data were obtained at 275, 293, and 303 K, yielding k(2) = (1.3 +/- 0.5) x 10(8) M-1 s(-1), (6 +/- 2) x 10(8) M-1 s(-1), and (8 +/- 3) x 10(8) M-1 s(-1), respectively. The atmospheric relevance of the chlorine hydrolysis reaction is discussed.