In a recent paper, Walker and Ulrych (1983) presented an algorithm for the recovery of the acoustic impedance from band-limited seismic reflection records. The approach used is based on the autoregressive (AR) modeling of the band-limited frequency transform of the data. This modeling procedure allows prediction of both the high and low missing frequencies. The low frequencies, which are particularly important in the inversion for the acoustic impedance, are determined by considering the low-frequency band as a gap of missing data which is centered at zero frequency. The gap is filled by minimizing the sum of the squared forward and backward prediction errors which result when the known spectral data are modeled as an AR process.