A rotary valve internal combustion engine has a piston (1) connected to a crankshaft (3) and reciprocatable in a cylinder (2), a combustion chamber (4) being defined in part by the piston. The engine has a rotary valve (5) rotatable in a valve housing (8) fixed relative to the cylinder (2), the rotary valve having a valve body containing a volume (9) defining, in part, the combustion chamber 4 and further having in a wall part (11) thereof a port (12) giving, during rotation of the valve, fluid communication successively to and from the combustion chamber via inlet and exhaust ports (13, 14) in the valve housing, wherein the rotary valve is rotatable about an axis (5a) parallel to the axis of rotation (3a) of the crankshaft, the valve being mounted in a bearing arrangement (7) which restrains the valve from movement in the axial direction but permits movement in the radial direction.