There is disclosed a chain transmission comprising a driving shaft provided with one or more sprockets and a driven shaft provided with complementary sprockets, which is coupled to the driving shaft via a chain. Preferably, two chain-moving elements are provided between the driving shaft and the driven shaft, near the sprockets, by means of which a desired transmission ratio can be set via axial movement of the chain. The chain-moving elements are movable over respective gear-shifting elements upon rotation of said elements, making it possible to shift from one sprocket combination to another with a reduced risk of malfunctions. The transmission is accommodated in a closed, self-supporting casing built up of interconnected casing members, in which the shafts in question are supported.