The analysis of CO2--δ13C--H2O--δD in vesicles of 35 submarine volcanic glasses reveals that open-system degassing, following closed-system degassing, is responsible for the observed variations in volatile concentration and isotopic ratios. The least degassed samples allow the assessment of minimum estimates for the flux of CO2 and H2O from the Pitcairn hotspot: 2.24 ¿ 0.17 104 tons C yr-1 and 1.32 ¿ 0.82 105 tons H2O yr-1. The results also suggest that the carbon in the source of the Pitcairn hotspot may have a δ13C value around -6?, 2? lower than the source of mid-ocean ridge basalts. This indicates either a possible contribution from the lower mantle or the possible involvement of decarbonated recycled materials with an unusual carbon isotopic signature.