Horizontal and vertical distribution of stress, in different layers of unbound materials of pavements, as well as stress in contact points between rock particles of these layers have been studied. Ring Chamber was used to study horizontal and vertical stresses under static vertical load. Stresses in contact points were measured using pressure films, placed in Ring Chamber. To investigate the influence of grain size on stress distribution, five size ranges of aggregates were tested. Analyses of the tested pressure films show very high stresses developed in some contact points due to the applied load. Variation in grain size of samples influences the stress distribution and that fine aggregates distribute stress more evenly than coarse aggregates. It has also been found that coarse aggregates have more roles in stress distribution and higher stresses developed in contact points between coarser aggregates.