To reduce the width of slabs from a reheating furnace to the width required in a finishing rolling train, thereby making it possible to feed slabs of only one width, or only a few widths, into the reheating furnace, the invention proposes rolling the slab in a width-reducing roll train in which the slab is subjected to traction such that plastic deformation occurs between the roll sets. In particular the width-reducing roll train has only one set of thickness rolls and has one or more sets of width rolls, thereby minimizing the length of the roll train and consequently reducing the lengths at the ends of the slab which are not subjected to the traction.