Ozone concentrations in the atmospheric boundary layer of the Pacific and Indian Oceans were measured on four separate oceanographic research cruises (July 1986, May to August 1987, April to May 1988). These measurements show a distinct zone of near zero (≤3 ppb) ozone concentration in the central equatorial Pacific in April--May, with ozone increasing in this region over the next 4 months. The seasonal observed change in the latitudinal gradient of ozone is consistent with previous ozone measurements at Hilo and Samoa by Oltmans and Komhyr <1986> and predictions from an atmospheric general circulation model study <Levy et al., 1985>. A significant diurnal cycle of ozone was found in almost all locations with a maximum near sunrise, a minimum in the late afternoon, and a peak-to-peak amplitude of 1 to 2 ppb (10--20%), similar to that predicted by a photochemical model in the low NOx limit <Thompson and Lenschow, 1984>. ¿ American Geophysical Union 1990