Comprehensive regulations to reduce the emissions of volatile organic compounds (VOCs), important O₃ precursors, were introduced in Japan in 2006. Analyses of the effect of the VOC reduction on high concentrations of O₃ have been required. Here, in the first place, we briefly review recently reported data analyses and model simulations relevant to the changes in the VOC and high O₃ concentrations. The O₃ level appears to be reduced, but it does not necessarily prove to be a direct result of the VOC reduction. Therefore, we propose a direct comparison of the change in the O₃ behavior in a group of days with high O₃ events before 2006 and another group of days after 2007 with very similar meteorological patterns to the former group. The result of the analysis for the Tokyo Metropolitan Area and its northern inland shows that, in the case of early sea breeze inflow to the inland area, the O₃ increase in the coastal urban area has become milder and that in the inland areas has not changed. Furthermore, for the late sea breeze, the situations of the O₃ increase have not clearly changed in any areas. If chemical transport models are utilized for an evaluation or an assessment of regulations such as VOC control, results of this kind of data analyses should be taken into consideration for productibility of the meteorological conditions and response to those changes.