Activities in a program to obtain thermodynamic data on compounds of interest in high-temperature chemistry are reported. Recent determinations were made concerning the heats of formation of UN, ZrH/sub 2/, and ZrD/sub 2/ using oxygen bomb calorimetry. Other results obtained by fluorine bomb calorimetry on TiF/sub 4/, HfF/sub 4/, and SiF/sub 4/ are also reported. (J.R.D.)