Abstract
Based on developmental formulations in different content areas of social cognitive functioning, a model and assessment procedure to determine adolescents' understanding of sexual behaviour was developed and psychometrically evaluated. A four stage model of sexual behaviour concepts was supported in a sample of 492 adolescents and young adults. The results showed the Sexual Behaviour Concepts measure has acceptable reliability (interrater, internal consistency, and test-retest) and construct validity in relation to age and Loevinger's measure of ego level development. There was no social desirability effect. Gender differences were in favour of females. The relevance of a construct of sexual behaviour understanding in the process of adolescent development was considered.