Ground level ozone concentrations were measured in Brazzaville (4¿20'S, 15¿20'E), Congo, from November 1983 to October 1984 and during shorter periods in other typical locations. The daily variations are of the same type as those observed at other weakly polluted continental sites. In the wet season the average concentration in the atmospheric boundary layer (30 ppb) is similar to that found over the Amazon tropical forest but higher than that found over the oceans. An ozone episode with maxima of about 70 ppb was observed; this episode may have had a photochemical origin. ¿American Geophysical Union 1987