Automatic (computer) correlation of geophysical logs is complicated by stratigraphic thickening (or stretch) from one area to another. Previous algorithms compute the stretch with repeated crosscorrelations of the original logs. Program SPECOR presented in this report uses crosscorrelation of the power spectra of the logs to identify the stretch factor between logs in one simplified operation. Computations are performed in the frequency intervals transformed to a logarithmic scale. Interpolation is required to obtain equally spaced power spectra. Given the stretch, displacement or lag between wells is computed rapidly by correlation processes, without needing to rely on iterative procedures.