Nuclear products which were caused by the D + D nuclear fusion reaction were searched in electrolytic cells and in gas phase of Pd + D systems. Measurements of nuclear products were made for gamma-ray, neutron, tritium and helium. To detect neutron, liquid scintillation and 3 He counters were used. For gamma-ray measurement, a NaI detector was used. For tritium concentration measurement in gas phase, a gas proportional chamber was fabricated and operated in low background level. The signals of those detectors were fed to Pulse Height Analyzer and recorded as energy spectra which were carefully compared with background spectra. A different type of neutron hunting was also tried in the instants of pressurizing and depressurizing the deuterium gas in crystal. A large size crystal of tungsten bronze was prepared for the experiment.