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Films of poly(R,R,R′,R′-tetrafluoro-p-xylylene) prepared by vapor deposition polymerization are highly crystalline and have uniplanar orientation. This orientation is maintained on drawing ×10 at 350 °C, when the chains become aligned parallel to the direction of draw, leading to a texture of threedimensionally oriented crystals. Thirty-five X-ray reflections are resolved by controlled rotation and tilting of the drawn specimen, and these can be indexed by a triclinic unit cell with dimensions a ) 5.36 Å, b ) 5.92 Å, c ) 6.57 Å (chain axis repeat), R ) 97.0°, β ) 63.1°, and γ ) 73.1°, containing one monomer unit. Molecular mechanics favors a trans-planar conformation for the -CF 2-CF2 linkage which is inclined at 90°to the adjacent phenyl groups, leading to a fiber repeat that is equal to that observed. Packing analyses point to a structure in which the phenyl groups are approximately perpendicular to the ac plane, and this gives good agreement between the observed and calculated structure amplitudes (R ) 0.18). The crystal structure is similar to that proposed for the R-form of poly(p-xylylene), except that the chain separation along the a axis direction is increased due primarily to the presence of the fluorine atoms.