Ball screw, having a spindle nut (1), on the inner circumference of which a helically wound ball groove (2) is formed, a return tube (4) being provided for balls (3), in which the balls are returned from an end to a beginning of the ball groove (2), lubricant channels (6, 9) provided with lubricant being formed on the inner circumference of the return tube (4), the injection moulded plastic return tube (4, 8) being longitudinally divided along a parting plane (E) into two half-tubes, the lubricant channels (6, 9) being arranged on both sides of the parting plane (E).