The actuator has a gear unit with a gear housing and a motor unit with a motor housing and an internally located rotor with a drive shaft, and a cylindrical bearing housing on the drive side. The bearing housing protrudes, along with a bearing and the drive shaft ducted therein, into an opening in the gear housing. The motor housing is flange-mounted, along with a drive shaft mounted therein, to the gear housing. The outside of the bearing housing and the inside of the opening in the gear housing have been geometrically mutually harmonized such that clamping points and tension-free places will form between them when the actuator has been assembled. The pretensioning force resulting therefrom produces a permanent frictional engagement between the outer circumference of the bearing and the bearing support or the bearing shell located opposite it. The operating life of an actuator of such type is increased.