In higher education admissions systems, different principles guide how students are selected when there is competition for study positions or when there is a limit on the number of students that can be admitted. The merit-based approach is very common in which the candidate with the best qualifications, or merits, is accepted. The way merit is defined and measured is, however, a complicated matter and reflects various views on validity and fairness. This chapter describes and discusses principles for the allocation of study positions, focusing on admissions practices where individuals are promoted or selected on the basis of their merits. Applications and challenges of such models, and the consequences for individuals, universities or colleges, and society at large are also discussed.