Evidence suggests that anomalies of functional organization in the brain may be present in some psychiatric disorders and that EEG differences between psychiatric patients and appropriate control groups may depend on them. It is therefore of practical importance to develop further ways of examining the association between the EEG and such organization. The change in inter-hemisphere coherence (a measure of EEG synchronicity) in the alpha frequency band when carrying out a task is shown to discriminate a group of II right from II left preferent normal individuals. Since right and left preference is associated with differences in cerebral functional organization, the coherence measure may be a useful way of studying this feature of psychiatric illness.