Guanidine reacts with cyclohexanone, cycloheptanone, acetone and 3-pentanone, resp., in a molar ratio 2:1 to give the 1,3,5-triazaspiroundeca- and dodeca-1,3-dien-2,4-diamines 3a and 3b resp. and the 6,6-dimethyl- resp. diethyl-1,6-dihydro-1,3,5-triazin-2,4-diamines 3d and 3e resp.On the contrary, action of guanidine on cyclpentanone yields not 3c, but the 1',5',6',7'-tetrahydrospiro-2'(3'H)-imines 2c, 5c and 6c resp., which are 1:2- and 1:3-condensates.Phenylacetone is transformed by guanidine (1:2) to give 6-phenyl-2,4-pyrimidindiamine (8f).The structure of the compounds cited is proved by NMR-, IR-, and (partially) mass spectra.The different courses of the formation of 3a, b, d, e, 2c, 5c and 6c resp. and 8f are also discussed.The structural formulae of some additional bases, which were synthesized from guanidine and cyclopentanone, 3-pentanone and phenylacetone resp. could not be established. - Keywords: Guanidine, reactions with ketones; Ketones, reactions with guanidine; 2,4-Pyrimidindiamine, 6-phenyl; Spiro-2'(3'H)-imine, 1',5',6',7'-tetrahydro; 1,3,5-Triazaspiroundeca- and dodeca-1,3-dien-2,4-diamine; 1,3,5-Triazine-2,4-diamines, 1,6-dihydro-6,6-dialkyl, and salts