Base-isolated active control is employed in this paper for the protection of tall buildings against strong earthquakes with application to a five-storey benchmark building model. The control system consists of a base isolation system (laminated rubber bearings) connected to an active control system (a tuned mass damper and an actuator). Linear functional observers are used to reconstruct the control signal for systems with a limited number of sensors. The effectiveness of the proposed control system is tested with different ground motions: El-Centro 1940, Hachinohe 1968, Kobe 1995, and Northridge 1994 earthquakes. Numerical results show that the rubber bearing system alone can perform well against Hachinohe, Kobe, and Northridge ground motions, but not well enough to protect the model against El-Centro ground motion. With an active control system implemented to the rubber-isolated model, significant improvements in earthquake resistance against these four earthquakes are obtained, especially against the El-Centro.