13C and 15N chemical shift anisotropy and 15N 1H dipolar powder patterns from backbone sites of the coat protein in fd bacteriophage are not averaged by motion. This means that the polypeptide backbone of the protein has no large amplitude motions rapid compared to 10 4 Hz. Relaxation studies on the 13C α and 15N amide resonances indicate the presence of motions on the 10 9 Hz timescale. These results are reconciled with a model where an otherwise rigid backbone undergoes small amplitude, rapid motions.