Consideration is given to arrays of cylindrical pin fins, with air entering the array at the plane of the fin tips, turning as it passes through the array, and exiting the array in crossflow. Per-fin heat transfer coefficients and overall pressure drops were determined experimentally. A computational model was formulated for determining the array heat transfer rates, with account being taken of the fact that the same rate of airflow does not wash over all of the fins in the array. The model was employed as a basis for comparing the heat transfer rates for various arrays operating at equal pumping power and equal baseplate to inlet-air temperature difference. The special foci of the work were to investigate the effects of various fluid inlet and exit geometries and also to utilize more closely spaced fins than in the past. It was demonstrated that partial shrouding of the inlet could give rise to nearly uniform per-fin heat transfer coefficients throughout the array. Modifications of the exit geometry affected only the less tightly packed arrays and then only at the outermost row of fins.