Abstract: An experimental study on fully-developed turbulent air flow in rectangular passages with two opposite rib-grooved roughened walls has been performed to determine the effects of the rib-grooved pitch-to-height ratios on friction factor and heat transfer coefficients. A general method for predicting average friction factor and average Stanton number in rectangular ducts with two smooth and two opposite rib-grooved walls is developed. Experimentalresults show that the performance of the heat transfer in the passages with rib-groovedroughened walls is better than that in the passages with rib roughened walls at the same s/h. This work may be useful to internal cooling design of the gas turbine blade.