Hydrothermal fluids from two vent sites along the East Scotia Ridge, E2 and E9, were analyzed for their hydrogen and oxygen isotopic values using a Picarro L1115-i CRDS. The fluids display varying salinity, sulfate and hydrogen sulfide content. None of the samples analyzed in this work showed any signs of spectroscopic interference. Isotopic values of the fluids were combined with salinity, magnesium and silica measurements to determine the possible role of magmatic inputs and phase separation. Oxygen isotope values (reported relative to VSMOW) range from -0.2 to +1.4 ‰ and hydrogen values range from -1.8 to +2.1 ‰. Oxygen isotope values of black smokers at each site differ on average by ~0.4 ‰. Relatively higher 18O values at E2 indicate water-rock reactions may be more prevalent here than at E9. Low salinity and D enrichment at E9 could indicate phase separation. Overall the data suggest that final fluid compositions reflect several complex processes during hydrothermal alteration.