Rankings have become a widespread phenomenon in an increasingly competitive world of higher education. They differ with regard to their aims, objectives, target groups, and with regard to their relationship to quality and quality assessment. Generally, rankings are an external assessment of the performance of higher education institutions; they enable transparency about systems of higher education. This paper discusses the relationship of rankings and quality assurance on an institutional and a system level. A clear conception of the differences between rankings and other forms of assessment of higher education institutions helps to understand the usefulness as well as the limitations of rankings and helps to prevent false or unrealistic expectations of rankings. (Contains 2 tables and 2 figures.)