2-Amino-4,6-dimethoxy-5-nitrosopyrimidine-water (4/3): seven independent molecular components are linked into a three-dimensional framework by six three-centre and eight two-centre hydrogen bonds.

In the title compound, 4C(6)H(8)N(4)O(3).3H(2)O, the pyrimidine molecules all exhibit a polarized molecular electronic structure; the seven-component asymmetric unit can be selected as a closed cyclic aggregate and the linking of these aggregates can be analysed in terms of translational chain motifs running parallel to [110], [210] and [011], which combine to generate a single three-dimensional framework.