This paper reports an experimental investigation on the effects of interfin spacing, shroud clearance, and missing pin on the heat transfer from cylindrical pin fins arranged in staggered and in-line arrays. The interfin spacing in the span wise direction was so small that the pins were almost touching each other. It was found that the optimum interfin spacing in both spanwise and streamwise directions is 2.5 D regardless of both type of array and shroud clearance used. The effect of missing pin for various interfin spacing arrays was found to be negligible for the in-line array but more significant for the staggered arrays.