Hydroxylamine and O-methylhydroxylamine react with phosgene to yield NN′-dihydroxyurea or NN′-dimethoxyurea. Dihydroxyurea forms a tetrabenzoyl derivative which gives O-benzoyl benzhydroxamate in hot aqueous ethanol. With phenyl isocyanate, dihydroxyurea gave hydroxydiphenylbiuret; with xanthydrol, xanthone and hydroxyurea were produced. Hydroxyurea and dihydroxyurea were determined colorimetrically with amminoprusside. In alkali, dihydroxyurea formed cyanate and hydroxyurea; hydroxyurea formed cyanate. Hydroxyurea was more stable than dihydroxyurea.