Abstract: A sheath (24) is provided for a syringe (10) having a barrel (18) with a needle assembly (22) projecting axially from the distal end thereof. The needle assembly (22) has a hub (28) with radially projecting ears (62) for threading into a collar (42) on the barrel (18). At least one axially extending, radially projecting rib (60) is carried by the hub (28). The sheath (24) has at least one camming flute (66) comprised of a flat circumferentially facing abutting surface (72) on one side and an axially and circumferentially facing cam surface (74) on the other side thereof. The sheath (24) frictionally grips the needle hub (28) with one rib (60) juxtaposed with respect to the camming flute (66). Rotation of the sheath (24) in one direction will engage the flat surface (72) with the rib (60) to rotate the needle assembly (22) with the sheath (24) for unthreading the needle assembly from the collar (42) on the barrel (18).