Formation shear wave attenuation (Qβ-1) and borehole fluid attenuation (Qf-1) values are estimated from the guided wave arrivals in full waveform acoustic logs. The use of guided waves avoids the problem of head wave geometrical spreading losses. Attenuation estimates are obtained from the inversion of guided wave spectral ratios using analytic partition coefficient expressions. The guided wave amplitude ratios are measured at uniformly spaced frequencies within a selected frequency window containing the pseudo-Rayleigh and Stoneley waves. Inversion of synthetic data from an open hole geometry results in Q estimates within 2--3% of the actual values. Inversion of cased hole synthetic data gives fluid Q and cement layer Q values within 2--3% of the actual values, but the formation shear wave Q estimate is in error by about 25% due to difficulty in identifying the pseudo-Rayleigh wave cutoff frequency from the amplitude spectra. Synthetic data results also indicate that the Q estimates are very sensitive to errors in any of the parameters that affect the partition coefficient calculations, such as the borehole fluid velocity or borehole radius. Application of the method to real data recorded in open boreholes provides reasonable results, but noise increases the variance of the Q estimates. ¿ American Geophysical Union 1987