Small-angle X-ray scattering (SAXS) experiments with in situ dehydration have been performed on small bundles of flax fibers. Analysis indicated that the structure of the cellulose microfibrils is consistent with a cross section of approximately 10 x 50 Angstrom(2). The microfibril misalilgnment was Gaussian with a full width at half-maximum of 11-15degrees, dependent on hydration level. A meridional peak at q = 0.095 Angstrom(-1) was observed, possibly for the first time in cellulose I fibers, and this has been attributed to a crystalline/noncrystalline repeat repeat distance of 60-70 Angstrom. It has also been noted that there is considerable change in structure as flax fibers dry from the wet state.