This thesis consists of four papers, all of which are concerned with the validation of selection to higher education. In paper [I] student performance was observed for a period of three years with a sample of three different admission groups. The purpose of the study was to see if there were any differences in academic performance between the three groups. The main result was that students admitted on the basis of their SweSAT scores and credits for work experience were less successful than the other two groups. In paper [E] the concept of validity is presented and discussed. The paper presents a historical perspective in the changed meaning of the concept of validity. In the paper, validity is also discussed in relation to qualitative and quantitative approaches. Paper [IH] was an attempt to apply a multi-faceted concept of validity to the Swedish model for selection. The results indicated that the assumption about unidimensionality of the components can be questioned, i.e. the unidimensional model for the SweSAT, GPA and the criterion for students achievement showed poor model-fit. This paper also briefly discusses the values that can be connected to the constructs that the instruments intend to measure. The result can be regarded as one explanation for the difficult-to-interpret picture resulting from an analysis of the predictive validity for the SweSAT and the GPA. In conclusion, the results indicate that a validation of a selection procedure does not produce any conclusive answers. Instead it raises important questions and issues that need to be considered for decisions about the applied selection procedure. In paper [IV] the concepts of fairness and justice are discussed in relation to selection to higher education. One central question in a validation procedure is the purpose of the selection. When the selection is viewed from the perspective of principles for distribution, several different principles can be identified. The relation between justice/fairness and validity is discussed. When the selection procedure aims to fulfill different purposes, and when the consequences are contradictory, this leads to a validity problem. Seen together, these articles constitute not only an evaluation of the Swedish selection, but also a methodological discussion of validity and validation practice. Overall, Messick's (1989) theoretical framework for the analysis of validity is judged to be a powerful instrument for the validation of assessment systems.