The thermal conductivity of single crystals of KMnF 3 , KCoF 3 , KNiF 3 , and KZnF 3 has been measured in the temperature range of 15° to 300°K by the absolute longitudinal heat-flow method. These compounds have the same crystal structure of the perovskite type and are antiferromagnetic except for diamagnetic KZnF 3 . The anomalous decreases are shown in the temperature dependence of the thermal conductivity for the magnetic crystals of KMnF 3 and KCoF 3 at their Néel temperatures of 88° and 114°K respectively, but KNiF 3 has no anomaly at its Néel temperature of 275°K. These anomalies are seemed to be due to the phonon-magnon scattering similarily to the cases of some magnetic substances. The diamagnetic KZnF 3 shows the normal behaviour of conduction, though the slope of the thermal conductivity versus temperature is somewhat lower owing to the impurity scattering of phonons than that being expected from Umklapp processes.