The rate constant for the reaction of HO2 with O-3 was measured using a turbulent flow reactor with tunable diode laser absorption detection of HO2. Two separate methods were used to determine k(1) from the pseudo-first-order decay of HO2 in excess O-3. The isotopic labeling method used (HO2)-O-18 in excess O-16(3) to avoid reformation of the reactant. The OH scavenger method used trifluorochloroethylene to remove the OH product and prevent re-formation of HO2. The turbulent flow reactor allowed measurements at temperatures between 297 and 197 K at total pressures from 80 to 175 Torr, spanning a wide range of stratospheric conditions. The temperature-dependent rare constant is given by the three-term expression k(1)(T) = {(103 +/- 57) exp[-(1323 +/- 160)/T] + 0.88} x 10(-15) cm(3) molecule(-1) s(-1), reflecting its non-Arrhenius behavior at low temperatures. These results demonstrate that the catalytic destruction of lower stratospheric O-3 by HOchi radicals (OH and HO2) may proceed faster than current models predict. The rate constant at 295 K is (2.0 +/- 0.2) x 10-15 cm3 molecule(-1) s(-1).