First atmospheric O2, CO2 and δ13C flask measurements from the high altitude site Jungfraujoch (JFJ), Switzerland, as well as from the mountain site Puy de D¿me (PUY), France are presented. The four-year records of JFJ and the three-year records of PUY show distinct seasonal cycles and superimposed long-term trends in the measured parameters. The mean peak-to-peak amplitudes of the respective seasonal cycles at JFJ are 79 per meg for O2/N2, 11 ppm for CO2, and 0.45 ? for δ13C. At PUY the seasonal variations are about two times larger than at JFJ. The spring time CO2 maximum at PUY appears in early march, whereas at JFJ it shows up 1 to 2 months later. The O2:CO2 correlation gives at both sites slopes of about -2 mol O2/mol CO2. Stable carbon isotope ratios of source CO2 show depleted values in wintertime and isotopically enriched values in summer.