An upright vacuum cleaner comprises a base assembly pivotally connected to an upright assembly. The base assembly comprises an agitator and an agitator drive assembly for selectively driving the agitator. The agitator drive assembly includes a drive disk coupled to a motor shaft, a driven disk which engages the drive disk, and a drive coupling between the driven disk to the agitator. The agitator drive assembly can further include a drive disengager for selectively interrupting the transmission of drive force to the agitator. The agitator drive assembly can further include a speed selector for adjusting the relative speed of rotation of the agitator.