A turbine blade, especially a turbine blade for the first or second stage of an industrial gas turbine engine, the turbine blade having an aft flowing triple pass serpentine cooling circuit with all convection cooled blade. The three passes or legs of the serpentine flow circuit are formed by a leading edge rib and a trailing edge rib that are both slanted in order to provide decreasing flow cross sectional areas in the three passes of legs. A mini serpentine flow circuit is formed on the blade tip and the beginning of the second leg of the circuit to prevent flow separation of the cooling air at the blade tip. The third leg of the circuit includes pin fins to promote heat transfer. A row of exit cooling slots are located along the trailing edge of the blade and are connected to the third leg to discharge cooling air out from the trailing edge region. Trip strips are located on the walls of the first and second legs to also promote heat transfer within these passages.