The objective of the investigation described in this paper was to obtain turbulent forced convective heat-transfer data for air flowing parallel to a flat plate with a stepwise discontinuous surface temperature. Heat was supplied by fifteen transverse nichrome ribbons on the upper and lower surfaces of a bakelite plate. The electrical input to each ribbon was controlled separately so that the surface-temperature distribution could be maintained constant or stepwise. Local heat-transfer coefficients were obtained from the measured ribbon temperature and the electrical heat input to each ribbon. The experimental results were correlated with the Colburn equation within ±6 per cent for a range of local Reynolds modulus from 60,000 to 800,000 by use of the starting-length correction of Rubesin (1). The starting length is defined as the position where the step occurs in the surface temperature.