In harmonic analysis using the DFT technique, the spectral leakage arises when the sampling procedure is not synchronised with the signal to be analysed. This paper presents a new algorithm to reduce this undesired effect. On the basis of an interpolation technique, the proposed algorithm tries to modify the actual sample sequence towards an ideal sample sequence that is synchronised with the signal. It is shown by theoretical analysis and computer simulations that the proposed algorithm can effectively reduce the leakage effect and thus improve the accuracy of harmonic analysis. © 1997 Elsevier Science B.V.