A detailed measurement of heat transfer and fluid flow of turbulent boundary-layer airflow in natural and mired convection adjacent to an isothermal vertical flat plate are reported. A cold-wire anemometer and laser Doppler velocimeter were used respectively, to measure simultaneously the time-mean turbulent temperature and velocity distributions and their turbulent fluctuations. In this experimental study, measurements of the flow and thermal fields were carried out at one streamwise location, x = 2.7 m, for a temperature difference Delta T of 30 degrees C between the heated wall and the free-stream air (with a corresponding focal Grashof number Gr(x) = 6.45 x 10(10)), and for a range of dimensionless free-stream velocities 0 less than or equal to U-infinity greater than or equal to 0.289. The effect of small free-stream velocity on the turbulent natural convection is examined These results reveal that when a small free-stream velocity is introduced on turbulent natural-convection pow, transition is delayed turbulence is suppressed, and the flow may relaminarize, causing the heat transfer rate from the heated wall to decrease.