Method and apparatus for providing an internal combustion engine which for each cylinder, with the associated piston, has at least one inlet valve and at least one exhaust valve (10) for controlling the connection between the combustion chamber in the cylinder and an intake system and an exhaust system, respectively. A rotatable camshaft (18) with a cam (22) is designed to interact with a first cam follower (17) and a second cam follower (20) in order to switch between two different operating modes. The cam followers are mounted on a pivotal rocker arm (13), the second cam follower (20) being hydraulically adjustable between two positions by means of a piston (21) located in a hydraulic cylinder. The hydraulic cylinder is connected to a hydraulic fluid source via a hydraulic fluid duct and the piston can be moved from one position to the other by the action of a quantity of hydraulic fluid delivered to the hydraulic cylinder.