Experimental results are presented for the effects of free-stream turbulence on the heat transfer through the turbulent boundary layer on a flat plate. An increase of wall friction with the consequent increase of the heat transfer was noted. From the mean-and fluctuating velocity values, different increase rates of the turbulent transport for the near-wall and the outer region are determined. The major part of tests were performed in air-flow. The ranges of Tu ≤ 0.2, Re_δ** ≤ 7·10³, Re_x ≤ 5· 10⁶ are covered. The analytical part was based on the hypothesis of mixing length.