Synthesis and properties of dinitrourea and its salts (NH4, hexamethyleneamine K) which have not been yet reported in literature, are described. DNU can be synthesized by nitration of urea with a high yield (>90%). Spontaneous decomposition of DNU and its salts below their melting points was noted during thermal analysis (DTA-TG). Low stability of DNU excludes the possibility of using it as an energetic material. Preliminary studies have shown that DNU can be used as a precursor in the synthesis of stable nitroamines.