Abstract: Apparatus for controlling the clearance between the tips of a row of rotor blades and an array of surrounding shroud segments in a gas turbine engine. A torque tube is rotatably mounted on the engine casing and has a cam positioned inside the casing. First and second members are positioned inside the casing so as to be only axially moveable and so as to have their cam-engaging surfaces axially surround the cam, and they are biased such that the cam-engaging surfaces engage the cam. A shroud hanger, to which a shroud segment may be attached, includes axially spaced apart hooked flanges positioned to be engaged by hooked flanges of the first and second members. The flanges have axially inclined slide surfaces for such engagement, and the shroud hanger is biased radially inward to engage such slide surfaces. Clearance is controlled by rotation of the torque tube which axially moves the first and second members which radially moves the shroud segment.