Disorders of interpersonal communication, as measured by a content analysis of the verbal behaviour elicited by a structured interview technique, were studied in a sample of 101 first admissions to a psychiatric hospital. Diagnostic groups were found to differ on several objective dimensions of verbal interaction. Schizophrenics had a lower total output of verbal units and they, as well as psychotics in general, had a lower over-all rate of usage of self (I, we) as the subject of their units. Selective verbal reinforcement of self-referred affect statements in one period of the interview produced an increase in the total output of verbal units, and a decrease during subsequent interviewer silence; these changes were more marked for the specific class reinforced than for other verbal units over the population as a whole. However, diagnostic groups differed in the extent to which their response to reinforcement was a specific change in output of self-referred affect statements or a non-specific change in other units. Ratings of the clinical EEG, based on the content of alpha and beta frequencies, also yielded groups which were significantly different in regard to their specific or non-specific verbal responsiveness in interview.