Total OH reactivity was measured in the suburban area, Tokyo, in July and August 2003, by use of a laser-induced pump and probe technique. More than 90% of the measured data of the OH loss rates were higher than the calculated values with simultaneously measured concentrations of various trace species. The maximum difference between the measured and calculated values is 34.3%. However, this difference was reduced to be 24.6% when using the rate coefficient of the OH + NO2 reaction recommended by IUPAC 1997, which is 40% larger than the most recently recommended value (JPL 2002). We concluded that this disagreement is due to the uncertainty of the OH + NO2 rate coefficient as well as existence of unmeasured VOCs. VOCs were quantitatively important as contribution to the OH loss processes.