Since October 2000, CO2 and water fluxes are measured within a young eucalypt stand in Congo. In this experiment, our main objective is to derive the net carbon ecosystem exchange (carbon sequestration) from continuous eddy flux measurements, and to compare these estimates to those obtained from 1) measurements of Net Primary Productivity (NPP) and soil heterotrophic respiration, and 2) measurements of carbon stocks (soil and biomass) and their variations over a chronosequence. Carbon stocks and soil respiration measurements were obtained over a chronosequence that includes 6 stands from 6 months up to 10 years within a 43000 ha massif of clonal eucalypt plantations established around Pointe Noire (4°S 12°E, Republic of Congo) over poor, sandy, and highly desaturated soils previously covered by littoral savannas. The Eddy correlation measurements were obtained from the top of a tower erected within the 3 year-old stand of the chronosequence. Soil CO2 efflux (monitored with a respiration chamber connected to a portable Li6200 infrared gas analyzer) exhibited strong seasonal variations, reflecting the seasonal changes in soil water content. Maximum values were obtained during the wet season, while minimum values were obtained in September-October at the end of the dry season (that lasts from June to October). Annual soil CO2 efflux was 11.8 t C/ha at Eddy correlation site, and 16.7 t C/ha at the 10 year old stand. At each site, good relationships were obtained between soil volumetric water content (measured from 0 to 6 cm from the surface) and soil respiration. The soil moisture effect on soil respiration was easily described by a 3 parameters equation. Rhizospheric and heterotrophic contributions to total soil CO2 efflux were estimated from comparison of soil CO2 efflux measured over trenched plots and soil CO2 fluxes measured over non-trenched plots: at the eddy correlation site (3 year-old stand), root respiration contributed to 26% of total annual CO2 efflux. Firs