This book presents research results from the international comparative study TIMSS Advanced 2015, which investigates the competence of students taking the most advanced courses in mathematics and/or physics in the last year of upper secondary school. This is the third TIMSS Advanced study in which Norway has participated. As a result, we have good data for analyzing trends in competence from the nineties until 2015 for the students in question, which we may call experts in these subjects.