Following Boyes and Chandler (1992), it is investigated how adolescents' epistemic understanding relates to the process of identity formation. In a cross-sectional as well as longitudinal study, identity status scores of diffusion, foreclosure, moratorium and identity achievement as assessed by the Extended Objective Measure of Ego Identity Status were analyzed as a function of adolescents' epistemic stance, while simultaneously taking into account individual differences in identity processing styles. The cross-sectional sample was composed of 200 German adolescents from Grades 7, 9, 11, and 13 (mean age: 16.2 years, SD = 2.41). The longitudinal study consisted of 134 participants (mean age at retest: 16.5 years. SD = 1.7) and covered a time interval of 18 months. Findings confirmed the view that the development of epistemic cognition contributes to adolescent identity formation. Specifically, the development of a multiplistic epistemic stance predicted higher moratorium scores, whereas the more advanced evaluativist epistemic position contributed to identity achievement over time. These effects were not due to individual differences in identity processing style.KEY WORDS: development of epistemological understanding; identity statuses; identity styles.