A study was made to determine the extent of the interference that may be expected in the operation of spacecraft science instruments when the spacecraft carries a radioisotope thermoelectric generator. Suitable analytical models were developed to predict the effects of the radiation spectrum on the various selected components. The gamma radiation was expressed as a 20-group structure between the energies of 40 keV and 10 MeV; the detectors selected for detailed evaluation were Geiger-Mueller tubes, continuous-channel electron multipliers, and silicon surface barrier detectors. The conclusions were that with reasonable separation between the radioisotope thermoelectric generator and the sensitive science components (∼15-ft) individual detectors would require a pound or less of shielding material in order that an acceptable spurious counting rate would be achieved. For a typical spacecraft payload, including such experiments as the cosmic-ray telescope, trapped radiation detector, and a lowenergy proton and electron differential energy analyzer, <10 lb of shielding would be required. Recommendations for developmental methods that could lead to means to reduce this amount of shielding were also made.