A series of laboratory model tests have been performed to study the behaviour of geocell-reinforced sand beds under strip loading. The strain in geocell walls, pressure transmitted to the subgrade soil, and deformations in the subgrade were measured during the tests to develop an understanding of the mechanism of geocell reinforcement. The pattern of strain variation in the geocell walls indicates that the geocell mattress behaves as a composite beam supported by the subgrade soil. The load dispersion in the geocell mattress is found to be governed by factors such as geometry of the geocell layer and its placement position under the footing. © 2007 NRC Canada.