A turbocharger system comprises a first relatively small high-pressure (HP) turbocharger and a second relatively large low pressure (LP) turbocharger. The turbine of the LP turbocharger is connected in series downstream of the turbine of the HP turbocharger in a first exhaust gas passage. An exhaust bypass flow passage provides a bypass flow path around the HP turbine. A rotary valve is located at a junction of the bypass flow passage and a first exhaust gas flow passage. The rotary valve comprises a valve rotor which is rotatable to selectively permit or block flow to the LP turbine from either the first exhaust gas passage or the bypass gas passage.