Hydrogen isotope fractionation between H2O and H-2 has been investigated at 313 K for sodium chloride solutions with salinities (S) ranging from 0 to 265 g.L-1. In the presence of a Pt catalyst, time needed to reach hydrogen isotope equilibrium between H2O and H-2 is close to 3 h (t(1/2) approximate to 30 min), independently on the salinity of the aqueous solution. Hydrogen isotope fractionation between H2O and H-2 increases with increasing molality (m) for a NaCl-like (sea salt) solution according to the following linear function: alpha(H2O-H2)(sea salt) = 3.387(+/- 8.4x10(-5)) + 3.4x 10(-3)(+/- 5 x 10(-5))m (R-2 = 0.997). The hydrogen isotope analysis of seawater samples with a salinity of 35 g.L-1 requires minor corrections of -2 +/- 0.5 parts per thousand (V-SMOW) whilst delta D values are overestimated by 5 +/- 0.5 parts per thousand to 10 +/- 0.5 parts per thousand in the case of highly saline natural waters (100