Abstract: A fluid-operated actuator (10) particularly for use in diesel-engined vehicles has a housing (12) defining a cylinder (14) having a cylinder wall (16) extending about a longitudinal axis (18). A piston (20) is arranged for reciprocal motion in the cylinder between a first end position and a second end position and an actuator rod (24) cooperates with the piston. The housing (12) includes first sealing means (28) for establishing a sealing contact with a first region (30) of the piston in the first end position and second sealing means (34) for establishing a sealing contact with a second region (36) of the piston in the second end position to thereby prevent leakage of operating fluid past the piston when the piston is in either of its end positions. To obviate e.g. the need for piston rings, the piston (20) and the housing (12) are arranged such that when the piston is between the first end position and the second end position, operating fluid is permitted to leak between the piston and cylinder wall (16).