Effects of complexation with water at three interaction regions on the CH stretching frequencies of N,N-dimethylformamide (DMF) are investigated based on IR measurements and quantum chemical calculations of DMF-water and DMF-chloroform-d mixtures. It is found that strong hydrogen-bonds on the carbonyl group make great contributions to the blue shift of C-H bond stretching frequency before hydrophobic hydration takes place. (C) 2004 Elsevier B.V. All rights reserved.