Gold-germaniump-njunctions for the detection of α-particles and fission fragments are reported in the References. The present investigation, using protons, deuterons, α-particles and He3ions, shows that the output pulse is proportional to the incident energy, providing the particle range does not exceed the effective junction thickness. Measurements on the maximum pulse heights obtainable from protons and deuterons agree on the effective junction thickness; however, the exact value varies with method and conditions of manufacture and increases with the voltage across the junction. The output pulse height is not dependent on the type of particle provided the junction bias is maintained above the minimum value (about 1 volt) required to prevent recombination. The pulse height is independent of crystal temperature if the voltage on the crystal is fixed, but as the temperature decreases the signal/noise ratio increases. At liquid-nitrogen temperature the resolution of 5 MeV α-particles (2–3%) is not determined by the signal/noise ratio. A value of 2.84 ± 0.12 eV, in accord with that previously reported, has been found for the energy required to produce an electron-hole pair in germanium. Pulse rise times have been shown to be less than 3 millimicrosec and are believed to be much shorter than this.Applications of these detectors in charged-particle spectroscopy are discussed.