This paper presents the results of a laboratory study on the lateral stress in a vibrated sand. No. 3 Ottawa sand was tested on a snaking table providing vertical vibration, and at-rest lateral stress was measured using a modified oedometer ring. The test results show that the lateral stress in normally consolidated sand increases with vibration time. The magnitude of the increase in lateral stress is related to the density of sand and the intensity of vibration. For overconsolidated sand with a high coefficient of earth pressure at rest, the lateral stress decreases with vibration time. Stress paths of a tested specimen are also presented in this paper. Key words : sand, coefficient of earth pressure at rest, lateral stress, vibration, overconsolidation ratio, stress path.