Condensation of aminomethy lene-malononitrile (1a) with aromatic aldehydes and dimethylformamide-dimethylacetal, resp., leads to benzylidene-malononitriles (2a, b) and to dimethylaminomethylene-malononitrile (2e), resp. A mechanism of this cleavage of a C=C double bond is discussed. Several substituted enaminonitriles (1e-i) are prepared and the reactivity against aldehydes is studied. Thus, condensation of 3-Amino-2-cyano-crotononitrile (1e) with aldehydes leads to 2-amino-4-phenyl-1,3-butadiene-1,1-dicarbo-nitriles (3). 4-Oxo-2-phenyl-1,2,3,4-tetrahydro-5-pyrimidine-carbonitriles (4) are yielded by the reaction of 3-amino-2-cyano-crotonic-carboxamide (1h) and 3-amino-2-cyano-cinnamamide (1i), resp., with aldehydes. Condensation of 1h and 1i with ethyl ortho-formate leads to 3,4-dihydro-4-oxo-pyrimidine-carbonitriles (6).