Combined x-ray diffraction/stereochemical structure refinement techniques were used in two separate studies. In one study, ramie fibers were analyzed directly after mild treatment with cellulase enzyme to improve the resolution of the diffraction diagrams. In the second study, the fibers were acetylated to cellulose triacetate without destruction of the fiber and the resulting crystal structure was determined. The results clearly show that ramie cellulose I is a parallel-chain structure nearly identical in detail with the more crystalline Valonia cellulose. The conversion to cellulose triacetate preserves the essential features of the cellulose structure. -- AATA