The turbulent fluxes of ozone and latent and sensible heat are computed from fast-response measurements made abroard a National Oceanic and Atmospheric Administration aircraft over downtown Philadelphia and the surrounding suburbs during the afternoon and evening of August 22, 1979. In the afternoon the ozone flux at a height of 200 m is downward throughout the region with the largest magnitude (-2(ppb)m s-1) occurring over the urban center. During the afternoon at both 200 m and a few hundred meters below cloud base, the horizontal profile of mean ozone concentration peaks at 130 ppb over the urban core with values of the order of 90 ppb to the southeast and northwest. The urban ozone condentration at 200 m decreases to 35 ppb by early evening. The normalized variances and spectra of vertical velocity, temperature, and ozone show little change with height or location in the urban center and northwest suburbs during the afternoon in good agreement with normalized statistics obtained over rural terrain (Kaimal et al., 1976); Lenshow et al., 1980). Data from a cloud penetration by the aircraft is used to estimate a mean updraft velocity of 4 m s-1 and an updraft area of approximately 1 km3. The flux of ozone due to the mean motion in the updraft is 2 orders of magnitude larger than the turbulent eddy fluxes within the cloud.