The following is a study of some aspects of the spin-locking effect in pure NQR. It was proved that the spin-locking effect similar to that obtained in NMR and based on the use of the frequency offset condition can be obtained in NQR. It was shown that the modified multi-pulse technique enable the observation of a long train of the spin-echo signals. The experimental results are presented for 4-cyanopyridine at room temperature. (C) 2007 Elsevier B.V. All rights reserved.