The available experimental reactor physics data related to problems of plutonium recycle have been reviewed and analyzed. Included were data from both basic lattice studies and irradiation experiments. It is concluded that there exists a reasonable amount of experimental data on clean lattice critical arrays. Extension of the data base to include more information on fine structure parameters would improve the usefulness of the experimental data base for testing design methods. The principal area where neutronic data are lacking is in the irradiation behavior of plutonium-fueled cores. The precision of the basic cross-section data for plutonium isotopes is reviewed. The precision to which the cross sections for the plutonium isotopes is known is nearly comparable to that for the uranium isotopes. On the basis of theory-experiment comparisons that have been published by several groups, the accuracy of existing calculational models needs to be improved. The principal area for improvement appears to be in calculating the thermal-neutron spectrum in plutonium-fueled systems.