MEASUREMENTS of the linear polarization of quasars at a wavelength of 49 cm (m49) have already shown that this parameter is correlated with spectral index α (ref. 1). We have now observed a more complete sample of 93 quasars, all of which have measured redshifts. The correlation between m49 and α is confirmed, but a further correlation has been detected, namely between m49 and redshift z. The relation between m49 and z is shown in Fig. 1. The redshifts are taken from Burbidge and Burbidge2, Schmidt3 and Hiltner et al.4. The spectral indices represent the spectral slope at or near 49 cm. The separation between flat spectrum and steep spectrum quasars is especially marked for low redshifts (z < 1.25). This separation does not exist for polarization measured at shorter wavelengths, and is therefore a depolarization effect, presumably by Faraday rotation within the source. Fig. 1 shows that the median value of m49 falls markedly as z increases for flat spectrum quasars. The median value of m49 is almost independent of z for steep spectrum quasars.