A motorized swivel truck for rail vehicles, especially streetcars, having a truck frame on which a cradle frame lying transversely of the direction of travel is supported by an air spring bellows, and the car body rests upon the cradle frame through an annular ball bearing which permits wide swiveling of the swivel truck. The swivel truck frame consists of two longitudinal members having a generally underslung configuration and whose middle, underslung portion has an open cross-sectional profile, and two transverse members which are disposed between the wheel axles and have a likewise open cross-sectional profile and which have a generally arched configuration, and whose ends are welded to the end portions of the longitudinal members. Owing to the underslung and arched configurations and the open crosssectional profiles the swivel truck frame is flexible, so that the wheel bearings may be mounted with very stiff springing in the end portions of the longitudinal members. The motor is suspended on the cross members by resiliently yielding means such that its drive shaft lies parallel to the direction of travel, the driving of the wheel axles is performed through a bevel gear transmission and a flexible coupling, and the air spring bellows are located adjacent the ends of the cradle frame.