We analyze the hydrogen budget of the lower stratosphere using simultaneous in situ measurements of northern hemispheric water vapor (H2O) and methane (CH4) obtained during the spring Stratospheric Photochemistry, Aerosols, and Dynamics Expedition (SPADE), as well as previously published in situ H2 data. Based on this data, we conclude that approximately two H2O molecules are produced for each CH4 molecule destroyed. This implies that H2 production from CH4 oxidation is balanced by H2 oxidation. The uncertainty in this analysis is greatly reduced by the use of multiple data sets. Additionally, we infer that, on an annual and global average, H2O enters the stratosphere with a mixing ratio of 4.2¿0.5 ppmv, and that the quasi-conserved quantity 2x[CH4>+[H2O> has a value of 7.6¿0.6 ppmv in these northern hemisphere air parcels (where [&xgr;> denotes the mixing ratio of the constituent &xgr;). ¿ American Geophysical Union 1994