A hybrid assay system utilizing both active and passive techniques has been built for the measurement of the plutonium fissile content in fast-breeder-reactor-type fuel pins. A moderated 252Cf source (∼600 µg) is used for the neutron interrogation of the fuel rods, and the fissile content is then determined by counting the high-energy delayed gamma rays resulting from the induced fission reactions. Neutron transport calculations using both Sn and Monte Carlo techniques were used to design the 252Cf neutron tailoring assembly to give an intense fast-neutron irradiation, as well as a high fissile/fertile fission ratio. In addition to the total fissile active assay, pellet-to-pellet uniformity is determined simultaneously by counting the lower energy passive gamma rays from the fuel using the same NaI detectors. The complete assay system, which includes automated fuel-rod handling and data reduction, is being used for in-plant measurements of Fast Flux Test Facility fuel pins.