The overall current density of Nb3Sn multifilamentary conductors heat-treated with hydrogen and argon is quite different. At flux densities above 11 T hydrogen samples carry more current than argon samples. below 11 T argon samples are superior to hydrogen samples. The transition temperature of hydrogen samples is generally found to be some tenths of a Kelvin below that one of the argon samples. X-ray investigations at room temperature indicate an increase of the lattice spacing in hydrogen samples corresponding to a growth of the unity cell up to 0.6% . The critical current of hydrogen samples undergoing tensile stress will increase in a way similar to argon samples.