The high activity of the radionuclides 65Ni (t1/2=2.52 h) and 58Co (t1/2=70.8 d) imposes severe limitations on the performance of direct instrumental neutron activation analysis of nickel. The extent of the interference of the 58Co depends on the ratio of the fluxes of the fast and thermal neutrons. A method of selective removal of cobalt, based on extraction with β-nitroso-α-naphthol has been developed for the purpose of radiochemical NAA. Separation yields have been determined for 36 elements. The detection limits obtainable with both the instrumental and the radiochemical method are <10−4 μg/g for the elements Au, Eu, Ir, La, Sc and Sm, between 10−4 and 10−3 μg/g for Cr, Cs, Hf, Hg, Lu, Re, Sb, Ta, Th, Tm and Yb, between 10−3 and 10−2 μg/g for As, Ag, Br, Ce, Ga, Na, Ru, Se, W and Zn, and in the range 0.01–1 μg/g for Ba, Cd, Co, Fe, In, K, Mo, Nd, Pd, Rb, Sn, U and Zr.