A broad-ranging investigation encompassing complementary experimentation and numerical simulation is performed to determine the pressure drop characteristics of arrays of diamond-shaped pin fins. The array geometrical parameters ST/W and SL/W, respectively, range from 1.15 to 2.00 and from 1.00 to 2.00, where W is the maximum fin width and ST and SL the transverse and longitudinal spacings. The investigated fins have forward-facing vertex angles of either 45 or 90 deg. The Reynolds number, based on the maximum fin width and the maximum fluid velocity, ranges from about 20 to 2200. From the experiments, highly accurate data for selected arrays are obtained for the per-row pressure drop, for the combined entrance and exit losses, and for the length of the hydrodynamic development region. The perrow pressure drop data served as a standard of comparison for the predictions of the numerical simulations, which are performed using a finite-element code applied to the periodic fully developed regime. The thusvalidated simulation model is employed to generate results for a wide range of geometrical conditions. To facilitate their application to design, the numerically determined per-row pressure drop results are correlated by compact algebraic equations (equations (12)-(15)).