419 patients (psychosomatic-C/L-service unit; neurotic spectrum, somatoform and personality disorders) were investigated by collecting data of clinical and psychometrical variables (SCL-90-R, NEO-FFI, IIP-D). The aim was to evaluate whether the sum score and the three factors of the German 20-item-version of the Toronto-Alexithymia-Scale (TAS-20) postulated by Bagby correlate with other clinical variables in a convergent way. The TAS-20 sum score and the factors (F1) "Difficulties identifying feelings" and (F2) "Difficulties describing one's feelings" correlated convergently with the NEO-FFI-scales "neuroticism" and "openness for new experiences", with numerous scales of the SCL-90-R, as well as with the scales "cool/repelling" and "introverted/social avoiding" interaction style of the IIP-D. Factor (F3) "Externally oriented thinking" correlated with "Extraversion" but was not related to clinical impairment (SCL-90 R). The results could be interpreted in terms of convergent validity of the TAS-20. In addition, alexithymic patients seem to be impaired with respect to interpersonal communication and they are subjectively able to perceive appreciate this restriction.