The anisotropy parameter ,?(~lv,,/ll.l) in phononlimited thermal resistivity of hexagonal metals at low temperature is estimated numerically from a very simple formula. It is shown that the thermal resistivity and electrical resistivity for these metals have a very different temperature dependence. As a result of this, the anisotropy parameter B for both Zn and Cd are found to decrease as temperature decreases, in agreement with experiment.