This study examines the construct validity of the 13-items Sense of Coherence (SOC) -instrument applied to a sample of 868 eighteen-year-old adolescents from a city in Sweden by using the Rasch model. All items showed relative invariance across the continuum, and although three items showed statistically significant lack of perfect invariance across genders, it was considered that they nevertheless worked sufficiently well to be retained. One item did show a response formal that was incompatible with the correct operation of the categories. The questionnaire could separate the adolescents from this general population and it was concluded that the results were consistent with Antonovsky's view that the SOC-scale should be dealt with as a measure of one global factor. (C) 2003 Elsevier Ltd. All rights reserved.