In twin roll casting of steel strip, molten steel is introduced into the nip between parallel casting rolls to create a casting pool supported on casting surfaces of the rolls and the rolls are rotated to deliver solidified strip downwardly from the nip. Casting surfaces are textured by a random pattern of discrete projections, which may have an average surface distribution of between 5 and 200 peaks per mm2 and an average height of at least 10 microns. In order to suppress chatter defects, the molten steel also has manganese content of at least 0.55% by weight and a silicon content in the range of 0.1 to 0.35% by weight. The strip is thus capable of moving away from the casting pool at a speed of more than 60 meters per minute without substantial high speed chattering defects.