This work was undertaken with the aim of determining the gas contents of zirconium carbide, niobium carbide, and tantalum carbide powders as functions of their processing history. A high-vacuum, high-temperature apparatus was used, connected to an oilless evacuation system and instruments for the mass-spectrometric measurement of amounts and compositions of gases being evolved. The specimens investigated were powders of various particle sizes poured into degassed molybdenum capsules with orifices. The results of this investigation into the effects of temperature and time on rates of gas evolution from carbide powders indicate temperature ranges of intense gas evolution. They will enable production engineers to choose conditions of vacuum heat treatment of powders so as to lower the gas content of finished parts and increase their density and strength. Diagrams and tables are included.