The reaction of ethoxymethylenemalononitrile (EMMN) with hydrazine hydrate in the presence of ethanol at room temperature gave 3-amino-4-cyanopyrazole (I) and a novel pyrazole derivative, 3-amino-4-cyano-2-hydrazonomethylpyrazole (II). When this reaction was carried out under reflux, II was not obtained. The result of various solvents for the preparation of II was found at present acetonitrile as a solvent most suitable. The reaction of EMMN with hydrazine hydrate in water at room temperature gave I in good yield. On the other hand, the reaction of hydrazine hydrate with excess EMMN afforded 7-amino-3, 6-dicyanopyrazolo [1, 5-a] pyrimidine.