This chapter aims to present the main models used for preference aggregation and decision support in a unified framework.After recalling the definition of a multicriteria decision making problem, we distinguish two approaches for preference aggregation:the compare then aggregate approach (denoted CA) and the aggregate then compare approach (denoted AC). We first present some procedures allowing the construction of an overall preference relation (e.g., a dominance or concordance relation) from several binary relations. Then we consider the AC approach and present some scalarizing functions allowing the definition of an overall score from partial numerical evaluations. In particular we review the min, Tchebycheff, OWA, WOWA aggregators and Choquet and Sugeno integrals.