||A simple moving box model was used to assess the effect of various control strategies on predictions of ozone formation in urban areas. It was found that the effectiveness of a proposed control measure depends critically on the ratio of the Volatile Organic Compounds (VOC) and NOx precursors that are emitted into the urban environment. Depending on the assumptions made about the ratio of the VOC and NOx emissions, a strategy involving simultaneous control of VOC and NOx can be more or less effective in reducing downwind ozone levels than a strategy involving reduction of only VOC. In all cases, however, it was found that NOx control, by itself, has a detrimental impact on ozone levels near source areas. Further, when NOx control accompanies VOC control, ozone concentrations near source areas are higher than would occur if VOC alone is reduced. NOx control, therefore, could result in greater population exposure to high ozone levels than would be the case if only VOC is reduced.