A method for roughening an inner surface (8) of a cylindrical bore (9), in particular a running surface in a cylindrical bore or cylinder liner of an internal combustion engine. A rotating tool (1) is moved in a translatory manner in the axial direction of the cylindrical bore (9) and has a radial cutting head (7). A chip (12) is lifted off by at least one cutting edge of the radial cutting head (7) and is broken away via a further edge or face of the radial cutting head (7), in order to produce the roughened surface. The tool (1) is introduced into the cylindrical bore (9) or is passed through it, after which a positioning of the tool (1) in the radial direction takes place, and after which the removal of the material takes place via the rotating tool (1) when the tool is moved in its advancing direction (V) out of the cylindrical bore. A tool (1) is also claimed.