A bearing assembly for an axle shaft of a vehicle. An inner ring includes a cylindrical body and an outer flange for mounting a wheel. On a portion of the cylindrical body adjacent the flange is mounted a revolution detection ring which has a seal contact portion and a gear-shaped detected portion having a plurality of projections circumferentially spaced on the outer peripheral surface thereof. The bearing assembly also has an outer ring which is coupled with the inner ring through rolling elements and mounted to the chassis of the vehicle. A sensor is mounted on the outer ring such that it confronts the gear-shaped portion of the revolution detection ring and detects the projections passing by the sensor so as to determine the annular speed of the wheel. The assembly also has a bearing seal which is mounted on the outer ring and kept in contact with the seal contact portion of the revolution detection ring so as to prevent contamination by sand, mud, or the like.