A mid-latitude northern hemisphere model of the daytime ozone distribution in the troposphere, stratosphere, and lower mesosphere has been constructed. Data from rocket soundings in the latitude range of 45¿N+15¿N, results of balloon soundings at latitudes from 41¿N to 47¿N, and latitude gradients from satellite ozone observations have been combined to produce estimates of the annual mean ozone concentration and its variability at heights up to 74 km for an effective latitude of 45¿N. This model is a revision for heights above 26 km of the tentative mid-latitude ozone model, included in the U.S. Standard Atmosphere Supplements, 1966, and has been adopted for use in the U.S. Standard Atmosphere, 1975.