Twelve subjects, six right-handers and six left-handers, participated in an experiment in which they were tested on an ipsilateral and contralateral auditory-manual reaction-time task. No difference in reaction-time was found between left and right ear presentation in the ipsilateral task, whereas for nearly all subjects, right-handers as well as left-handers, a difference between the left and right ear presentation was recorded in the contralateral task. The right-handers showed a tendency to a right ear preference, the left-handers to a left ear preference. The results are discussed in terms of a combination of S-R compatibility and the cerebral organization in man.