The effect of chelating agents on the determination of cobalt in various flames, in a graphite cuvette and tantalum boat was studied considering the expected reaction mechanism of the atomization of cobalt and the reagent donor atom. A marked increase in the sensitivity of the determination of cobalt was observed in the presence of 1-(2-pyridylazo)-2-naphthol, pyrrolidinedithiocarboxylate, diethyldithiocarbamate, 8-mercaptoquinoline, 8-hydroxyquinoline and thenoyltrifluoroacetone for atomization from a tantalum boat. The optimum conditions for the determination of cobalt in the presence of 1-(2-pyridylazo)-1-naphthol are given.