Abstract: A blade tip shroud structure for a compression stage of a gas turbine engine is disclosed. Various concepts relating to shroud designs and their influence on blade performance are discussed. In accordance with the teaching contained herein, one shroud geometry includes a circumferentially extending recess in the wall of a case which circumscribes the tips of the blades. A surface at the bottom of the recess has discontinuities therein. The tips of the blades run line on line with the respective wall at the design operating condition of the engine in which the shroud structure is incorporated. In one embodiment axially skewed grooves and circumferentially extending grooves form the surface discontinuities.