Intermolecular multiple-quantum coherence (iMQC) signals between spin-1 nuclei in liquid nuclear magnetic resonance (NMR) were observed for the first time using the modified CRAZED pulse sequences. Signal expressions were derivated from density matrix treatment. Experiments were performed on a deuterated two-component system to determine the optimum RF pulse flip angles for the iMQC signals between spin-1 spins. It is found that the optimal RF pulse flip angles for the strongest iMQC signals from the spin-1 system are identical to those for the spin-1/2 system. Theoretical results are in excellent agreement with experimental observations. (C) 2009 Elsevier B. V. All rights reserved.