A valve operating mechanism for operating a plurality of valves of a particular cylinder of an internal combustion engine includes a camshaft rotatable in synchronism with rotation of the internal combustion engine and having at least one cam. At least one of a plurality of cam followers slidably engages the cam for selectively operating the valves according to a cam profile of the cam. The cam followers are selectively interconnected and disconnected to operate the valves in different speed ranges of the internal combustion engine, the speed ranges including a range in which all of the valves remain inoperative. The camshaft has one or two annular raised portions in addition to the cam, and the cam followers include one or two cam followers which slidably engage the raised portion or portions. The valves remain inoperative by the annular portion or portions and are operated in a high-speed range by the cam, or selectively in low- and high-speed ranges by low- and high-speed ranges.