The X-ray structure of the 1:2 host-guest complex between 1,4,7,10,13,16-hexaoxa-cyclooctadecane (18-crown-6) and 2,4-dinitrophenylhydrazine is reported. Crystallo-graphy data are: space group P21/c, a = 8.557(2), b = 16.745(6), c = 12.387(4) Å, β = 117.08(13)°, Z = 2, Dm = 1.37 g · cm-3 , Dc = 1.387 g · cm-3 , m.p. 414 K (decomp.). The present B is 0.11 for 1733 diffractometer data. In the complex, the two 2,4-dinitrophenylhydrazine molecules are located "above" and "below" the plane of the hexaether and related by an inversion centre. They interact with the macrocyclic host via N-H···0 hydrogen bonds, two of which are bifurcated. All the ether oxygens of the crown serve as hydrogen bond acceptors.