Comparisons of calculated and measured neutron balance components are reported for the 7. 5% fissile plutonium reference test lattice of the PROTEUS-light water high conversion reactor (LWHCR) phase II program, both wet (with H//2O) and dry (100% void). Special experimental techniques have been developed and applied, particularly for k// infinity , and the range of directly measured reaction rate ratios has been extended. For the two cell codes tested, WIMS-D/1981 library and KARBUS/KEDAK-4, specific shortcomings have been identified; the new measurements have been found to be significantly more representative and accurate than the earlier phase I experiments.