In the interaction of 3-hydroxyiminopentan-2,4-dione with isopropylamine or cyclohexylamine are formed Schiff base (3-hydroxyimino-2-iminoketones). Based on the visible, I.r., 1H и 13C NMR, 1H-13C НМВС и 1H-15N НМВС spectral data "backbone" structures of 4-isopropylimino-3-hydroxyiminopentan-2-one and 4-cyclohexylimino-3-hydroxyiminopentan-2-one elucidated. The influence of the structure of Schiff bases on the tautomeric equilibrium in chloroform between hydroxyimino-iminoketones and nitroso-enaminones forms are discussed.