A method of treating hot metal slabs (6) aims to reduce the width of the slab (6) produced by a continuous casting process to avoid the need for the prolific number of moulds otherwise required to produce slabs of various widths. In order to achieve this the hot metal slab (6) is presented, with its width dimension vertically oriented, to a pressing machine (24) having a vertically movable top platen (26) and a fixed bottom platen (28). The slab (6) is incrementally displaced, longitudinally, through the pressing machine and pressing forces are applied to its opposing edges by the platens, to reduce its width. Subsequently, the slab (6) is turned so that its width dimension is oriented horizontally and rolled between the horizontal rolls of a rolling mill (22). An apparatus for performing the method is disclosed.