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The distributions of the CO2 partiala pressures in surface seawater and in atmosphere are shown and analysed in the tropical Atlantic during the period from July 1982 to August 1984 for both extremal seasons (summer and winter). The comparison between the 1983 results and the 1984 results puts in light the anomaly of the atmospheric conditions which prevailed above the equatorial Atlantic area during 1984, and which induced anomalous hydrological features and surface oceanic circulation (Hisardet al., 1986). The variability of the oceanic CO2 partial pressure seems nearer the one of salinity than the one of temperature. The leading part of the lateral advection against the vertical motion as the main mechanism responsible for high PCO2 waters is underlined. In some places (north of the equatorial belt 5°–5°S), nevertheless, it is possible to relate the PCO2 variations with the temperature variations of the surface layer. Along the equator, in the surface layer, there is a loss of CO2 corresponding to the CO2 evasion through the ocean-atmosphere interface—this loss is larger in the western part than in the eastern part. The CO2 evasion flux, which can be determined under some circumtances, is near the net CO2 flux calculated by the gradient method for the same period. The results of CO2 flux by the gradient method vary largely (ratio ∼ 5) with the approach followed to determine the gaseous transfer coefficient through the interface. As the evaluations of the net CO2 flux are approximate, we examine another approach based upon the empirical relationship found between PCO2 and salanity to determine the gradient of PCO2 through the interface and then the net CO2 flux: this approach yields an acceptable uncertainty (±25%) for teh net CO2 flux. A large north-south gradient of the atmopheric CO2 is observed every year during boreal winter above the equatorial belt (5°N–5°S)—it is related to the Intertropical Convergence Zone of the trade winds. The mean atmospheric CO2 growth rate calculated during the 1982–1984 period is less (0.6 ppm y−1) than the secular trend CO2 levels (1.2–1.5 ppm y−1).