5,6,7,8-Tetra-hydro-[1,2,4]triazolo[5,1- b ]quinazolin-9(4 H )-one.

The triazole ring in the title mol-ecule, C 9 H 10 N 4 O, is not quite coplanar with the six-membered ring to which it is fused, the dihedral angle between the two least-squares planes being 2.52 (6)°. In the crystal, a layered structure is formed by N-H⋯N and C-H⋯O hydrogen bonds plus slipped π-stacking inter-actions, with the fused cyclo-hexene rings projecting to either side.