In recent years there has been much attention to the study of ear differences in the response to auditory stimuli. However, the possibly of ear differences in auditory adaptation effects has apparently not been investigated. The present authors used a monaural heterophonic balance to investigate the adaptation of a 500 Hz adapting tone. Ten subjects were tested in the left ear, ten in the right. Left ear adaptation was 4.20 dB, while right ear adaptation was 12.88 dB (p is less than or equal to .001). Previous differences in binaural adaptation studies could conceivably have been partially influenced by the ear adapted. It is suggested that the possibility of ear differences in loudness adaptation be taken into account in future studies.