The magnetization behaviors of La0.7-xYxPb0.3MnO3 (0.0.LEQ. x.LEQ. 0.2) have been examined. The replacement of La ions by Y results in a considerable decrease in the ferromagnetic ordering temperature TC and irreversible behavior in the zero-field cooling and field cooling curves at a low applied field. The saturation magnetization MS decreases as Y content increases. The results can be explained by the suppression of ferromagnetism due to structure tuning induced by the substitution of Y into the La site.