This report has been prepared as part of Task 5.2 of the SAMARIS project, which deals with the prediction of rutting of unbound granular pavement layers. It presents a literature review of models for the prediction of permanent deformations of unbound granular materials, in order to select appropriate models for the SAMARIS project. The report describes first some general aspects of the behaviour of unbound granular materials, and makes a review of available models to describe permanent-deformation behaviour. Both simple, empirical relationships and more elaborate incremental, elasto-plastic models are reviewed. Then, several models are selected and evaluated, by comparing their predictions with results of existing repeated load triaxial tests. Based on this evaluation, two models are selected for the modelling work in SAMARIS. Finally, methods for applying these models for calculation of rut depths in pavement structures are discussed.