The aims of this study were (i) to define the dimensions of non-verbal behaviour which distinguish between schizophrenic patients and control subjects and (ii) to examine the relationship between patients' non-verbal behaviour and clinical symptoms. The non-verbal behaviour of 28 drug-free patients with schizophrenia according to Research Diagnostic Criteria (RDC) and 25 control subjects was videotaped during interviews and scored according to an ethological scoring system. Patients' symptoms were rated on the Scale for the Assessment of Negative Symptoms, the Scale for the Assessment of Positive Symptoms and the Brief Psychiatric Rating Scale. As a group, schizophrenic patients showed a global restriction of non-verbal expressiveness, as indicated by their lower scores on prosocial behaviour, gesture and conflict. However, some patients had normal ethological profiles. Non-verbal behaviour was largely independent of negative and positive symptoms. Deficits in non-verbal behaviour may play a role in determining or aggravating dysfunctional patterns of relating in schizophrenia. Ethological analysis provides further support for the model that conceptualizes positive symptoms, negative symptoms and disorders of social relationships as three separate dimensions of the schizophrenic syndrome.