Phase I integral experiments of U.S./JAERI Collaborative Program on Fusion Breeder Neutronics which were carried out at the Fusion Neutronics Source (FNS) facility at JAERI ranged from D-T neutron source characterization experiments, tritium production rate (TPR) measurements in a reference Li2O assembly, first wall experiments with and without coolant simulation and beryllium neutron multiplier experiments in various configurations. Both U.S. and Japan have independently analyzed these experiments using their own data base and codes. Analytical predictions obtained by both countries were compared to measured values. Results of this intercomparison is presented in this paper.