The segregation phenomena of different binary mixtures were studied experimentally in a vertical shaker. The larger particles tend to move upwards in the shaker in a certain range of vibrational accelerations. The segregation effect was more significant for the mixture with a larger size difference. The segregation coefficient was measured and found to increase with vibrational acceleration until reaching a maximum and then to decrease with acceleration. The bed expansion height was also measured. It was found that the greatest segregation effect occurred when the bed transformed from a dense state to a loose state.