Tantalum carbide sinters at a temperature above 2500‡C. Decreasing the powder particle size activates the sintering process, but even with a powder of 0.17-Μm particle size specimens sintered at 2700‡C have a porosity of 11%. Coarse powders (> 7–8 Μm) sinter, without densification, at 2000–2200‡C by a surface self-diffusion mechanism. Fine powders (<7–8 Μm) undergo densification already at temperatures above 1400‡C by a diffusion-viscous flow and a volume self-diffusion mechanism during long holding periods and also probably by an activated grain-boundary sliding mechanism in the initial stage of sintering after rapid heating.