BACKGROUND: Recently, the Toronto Structured Interview for Alexithymia (TSIA) was developed to supplement the self-assessment of alexithymia and/or offer a different method of measuring the alexithymia construct. The aim of this study was to evaluate the psychometric properties of a German language translation of the TSIA in a psychiatric patient sample. METHODS: Translation and back-translation were performed until a high agreement of cross-language equivalence was obtained between the German and the original English language version of the TSIA. The TSIA and the German language version of the 20-Item Toronto Alexithymia Scale were administered to 237 psychiatric patients at the departments of psychiatry and psychotherapy in Germany and Switzerland. Videotapes of some of the interviews were recorded for the assessment of interrater reliability. RESULTS: The German version of the TSIA and its 4 scales correlated significantly with the German version of the 20-Item Toronto Alexithymia Scale and its 3 factor scales, providing support for concurrent validity of the interview. Confirmatory factor analyses supported the hierarchical, 4-factor structure obtained with the original English version, with 4 lower-order factors nested within 2 higher-order latent factors. Acceptable levels of internal reliability and interrater reliability were also demonstrated. CONCLUSION: The TSIA is a valid and reliable measure for assessing alexithymia, at least in clinical samples. The TSIA, together with a self-report alexithymia scale, allow for a multimethod approach to assessing alexithymia.