The distribution of ozone in the African tropical region is examined for measurements made between late June 1990 and early October 1992 in support of the NASA Global Tropospheric Experiment/Transport and Atmospheric Chemistry Near the Equator-Atlantic (GTE/TRACE A) experiment conducted at Brazzaville (4¿17'S, 15¿15'E) in September and October 1992. A set of ozone data has been obtained in the troposphere and the stratosphere to above 30 km using balloon-borne electrochemical concentration cell ozonesondes. The analysis of the tropospheric data confirms the seasonal trends of ozone in these latitudes, which shows in particular, the presence of an ozone-enriched layer located between 1- and 4-km altitude during the dry season of each hemisphere. A more detailed analysis of the data set for September--October 1992 shows a behavior of ozone which suggests the presence of two periods of biomass burning in the dry season of the southern hemisphere. In addition, this study shows that the dry season of the northern hemisphere has a limited influence on tropospheric ozone at large distances. ¿ American Geophysical Union 1996