A portable Gamma-Ray Spectroscopy system has been designed and tested for identification of nuclear materials in the field. A P-I-N CdZnTe detector was developed to minimize the leakage current and to improve energy resolution. The detector has a sensitive volume of 200 mm3 and has been constructed with novel heterojunction contacts. Thermoelectric cooling is used to reduce leakage currents in the detector element and the input thermal noise to the FET. Risetime discrimination is used to offset the negative effects of incomplete charge collection. The detector probe is connected to a single unit comprised of detector electronics, an MCA and a portable computer, all operated from battery power. Results from testing with laboratory radioisotopic sources are presented.