The present work submits an investigation about the effect of the geometric position of wall mounted rectangular blocks on the heat transfer from the surface, taking into account the angular displacement of the block in addition to its spanwise and streamwise disposition. The experiments were conducted with air in a rectangular channel. The blocks with 1 x 2 x 2 cm(3) dimensions were mounted on a heating surface. The experimental ranges of the parameters were S-x = S-y = 3.33-4.33 mm, alpha = 0-45 degrees, and Re = 1520-4520 based on block length. In the experimentation, a Taguchi method was employed, and the results showed that the most efficient parameters were Re and, then, angular disposition. In the experimental range, S-x and S-y, have a slightly increasing effect on the heat transfer. The results also proved that the Taguchi method can successfully be applied to this kind of study, and the prediction of the method was in very good agreement with the experimental result. (C) 2001 Elsevier Science Ltd. All rights reserved.