Recent progress in protein spatial structure determination by NMR has relied largely on the ability to record two-dimensional ‘H spectra in Hz0 solution (I-3). At various stages of the investigation of a protein one makes use of the fact that in a homonuclear proton correlated spectrum (COSY) there is one amide proton-C* proton cross peak for each amino acid residue (two for glycine, none for proline), which altogether constitute the “fingerprint” of the protein (4). Although at low pH the amide protons usually exchange sufficiently slowly with the solvent to be observed with water suppression by continuous selective irradiation, there may still occur some “bleaching” of crosspeaks in the fingerprint region of a COSY spectrum due to saturation of C”H signals under the water line (I-3). The.present note proposes the use of doublequantum spectroscopy (DQ spectroscopy) for the observation of complete protein fingerprints (5). Observation of a complete fingerprint while applying a saturating pulse on the water resonance relies on the fact that double-quantum coherence is excited starting either from C”H or NH. Apart from a different coefficient due to additional passive couplings with the C@ protons, initial C*H magnetization leads to the same DQ coherence as initial NH magnetization, for which the evolution in the course of the DQ experiment (?r/2-7/2-?r-T/2-?r/2-tl-B/2-acquisition) is described in the following in terms of product operators (6)