Abstract: In a zoom lens the fixed barrel is provided with one or more smooth outer surfaces on which are slidably supported an operating member supporting a first lens system and a driven member supporting a second lens system. A linear slot and a first oblique cam slot are formed in one or the other of the outer barrel surfaces and a second cam slot is formed in the operating member. The operating member slides in the linear slot, and pin means on the driven member engages the two cam slots. This mechanical arrangement permits movement of the lens systems frame a wide-angle to a telescopic position and vice versa. Since all sliding movement is on the outside of the barrel, applied lubricant does not fall inside the barrel and the inner surface of the barrel may be treated in any suitable manner to prevent internal reflections.