Over many years NPL has carried out measurements of surface tension of steels using the levitated drop method. Much of this work has been to study variations in weld profile brought about by changes in Marangoni flow patterns in the liquid pool, and many of these data have remained unpublished. 49 ferritic and austenitic steels are compared, and relationships for surface tension, and the coefficient of surface tension against temperature, based on sulphur content of the steel, are presented. Data has been reassessed using the Cummings correction to allow for the effects of the levitation forces. (C) 2005 Springer Science + Business Media, Inc.