The authors assessed, in an adolescent population sample, the internal consistency, test-retest stability, and factor structure of the Toronto Alexithymia Scale (TAS-20) and established the frequency of alexithymia in this age-group. Pupils (N=882; age-groups: 14-, 15-, and 16-year-olds) from two secondary schools completed the TAS-20 questionnaire twice, with a 5-week interval, in a classroom survey setting. TAS total and subscale scores and proportion of subjects exceeding the cut-point for alexithymia are reported for boys and girls. In confirmatory factor analysis, all estimates except one item were statistically significant; there was no gender difference. The authors conclude that the TAS-20 has good psychometric properties in adolescent samples. Alexithymia rate decreases from early to middle adolescence and remains essentially on a level similar to that among adults.