The relative motion between a ball bearing outer race and the bearing's cartridge was investigated. The investigation was part of a larger program, the objective of which is to examine the important parameters influencing fretting corrosion in rolling element bearings. The bearing examined was a 320 size, deep grooved, ABEC 7 ball bearing used in a Navy ship service motor-generator unit. Three axes of acceleration signatures were simultaneously recorded from the outer race and cartridge. These acceleration signatures were Fourier transformed, averaged, and integrated twice to obtain displacement frequency spectrums. Corresponding displacements were vectorially subtracted to produce the relative motion between the outer race and the cartridge. Two load cases (0% and 100% load) and two frequency ranges (15 to 500 Hz and 30 Hz to 10 kHz) are examined. The resulting relative motion spectrums were complex with the bearing's forcing frequencies dominating the spectrums below 250 Hz and rotor imbalance causing the highest spectral component of relative displacement (170 µm). / M.S.