[en] The partial pressure of CO2 (pCO2) and dissolved oxygen saturation level (%O2) were monitored continuously during a cruise in August 1998, which sampled surface waters off the Galician coast. Data are presented from two Lagrangian experiments carried out in an upwelling on the continental shelf and in the core of an offshore filament. The data show that daily variations in surface pCO2 and oxygen (%O2) were controlled by the diurnal cycle of primary production/respiration, temperature variations and air–sea exchange. Data obtained during various cross-shelf and cross-filament transects are also discussed and give an insight into the processes controlling large scale variations of pCO2 and %O2 in the Galician upwelling system. These data suggest that upwelling filaments are an important feature of the inorganic carbon cycle of upwelling systems. However more field data in the various eastern boundary current systems worldwide are needed.