Fractionation of the noble gases should occur during formation of a Structure I gas hydrate from water and CH (sub 4) such that CH (sub 4) hydrate is greatly enriched in Xenon. Noble gas concentrations and fractionation factors (F[ (super 4) He], F[ (super 22) Ne], F[ (super 86) Kr], and F[ (super 132) Xe] as well as R/R (sub a) ) were determined for eight gas hydrate specimens collected on Leg 164 to evaluate this theoretical possibility and to assess whether sufficient quantities of Xe are hosted in oceanic CH (sub 4) hydrate to account for Xe "missing" from the atmosphere. The simplest explanation for our results is that samples contain mixtures of air and two end-member gases. One of the end-member gases is depleted in Ne, but significantly enriched in Kr and Xe, as anticipated if the source of this gas involves fractionation during Structure I gas hydrate formation. However, although oceanic CH (sub 4) hydrate may be greatly enriched in Xe, simple mass balance calculations indicate that oceanic CH (sub 4) hydrate probably represents only a minor reservoir of terrestrial Xe. Noble gas analyses may play an important role in understanding the dynamics of gas hydrate reservoirs, but significantly more work is needed than presented here.