[1] The column-average dry air mole fractions of atmospheric carbon dioxide and methane (X CO 2 and X CH 4 ) are inferred from observations of backscattered sunlight conducted by the Greenhouse gases Observing SATellite (GOSAT). Comparing the first year of GOSAT retrievals over land with colocated ground-based observations of the Total Carbon Column Observing Network (TCCON), we find an average difference (bias) of −0.05% and −0.30% for X CO 2 and X CH 4 with a station-to-station variability (standard deviation of the bias) of 0.37% and 0.26% among the 6 considered TCCON sites. The root-mean square deviation of the bias-corrected satellite retrievals from colocated TCCON observations amounts to 2.8 ppm for X CO 2 and 0.015 ppm for X CH 4 . Without any data averaging, the GOSAT records reproduce general source/sink patterns such as the seasonal cycle of X CO 2 suggesting the use of the satellite retrievals for constraining surface fluxes. Citation: Butz, A., et al. (2011), Toward accurate CO 2 and CH 4 observations from GOSAT, Geophys.