The Mn content of 18 natural diamonds, and the Na and Cu content of 7 of the specimens, was measured quantitatively by neutron activation analysis. Gamma- scintillation spectrometry was used to detect the 0.85-Mev gamma emission of Mn54, the 1.37-Mev gamma emission of Na24, and sion of Cu64. The specimens examined weighed between 5 and 100 mg, and the levels of impurity found were 0.002 to 0.09 ppm of Mn, 0.05 to 0.4 ppm of Na, and less than 0.0004 to 0.9 ppm of Cu. The precautions taken to avoid errors due to self-shielding and various forms of interference are discussed.