A substantially self-contained vibration control system for building structures. A building has mounted on its roof, or an upper level floor, a hollow concrete-steel first mass carried on high damping rubber supports. Within the hollow of the first mass a second mass is mounted on anti-friction rollers which roll on a low coefficient of friction interior floor of the first mass. The first and second masses are interconnected with a single means to vibrate these masses with a period of vibration which can be synchronized with the vibration period of the building to attenuate building vibration.