A detailed validation study of the SDX fast reactor cell homogenization code, Benoist anisotropic diffusion coefficients, and an associated three-dimensional to one-dimensional unit cell modeling procedure has been in progress. These earlier results have investigated the standard zero power reactor (ZPR) plate-type unit cell The present study represents a complimentary validation effort for the ZPR pin calandria-type unit cell. The unit cell loading selected for this work consisted of a 5.08- × 5.08- × 30.48-cm voided calandria loaded with a 4 × 4 array of 0.957-cm (diam) × 15.24-cm mixed-oxide rods (15% PuO2/UO2). This unit cell was used in the pin zone measurements of the ZPR gas-cooled fast reactor program and also in the sodium-voided pin zone measurements of ZPR-6 Assembly 7. The validation effort consists of direct comparison with results of VIM (continuous energy Monte Carlo) calculations. The SDX/Gelbard methods have been shown to adequately predict both nonleakage and leakage effects for the voided pin calandria unit cell.