The carburization of B-niobium oxide (B-Nb2O5) to niobium carbide (NbC) in 20% (v/v) CH4/H2was studied at temperature-programmed conditions. The reaction required high temperatures, greater than 1370 K, and variations of heating rate (0.04–0.17 K s−1) and molar space velocity (400–1600 h−1) had only a minor effect on the product specific surface area (Sg). In the course of the transformationSgincreased from 1 m2g−1to about 20 m2g−1, and scanning electron microscopy showed the development of macropores of about 100 nm. The progress of the reaction was followed by mass spectroscopic analysis of the gaseous products, which identified two distinct stages. X-ray diffraction analysis of reaction intermediates showed that in the first stage B-Nb2O5was reduced to NbO2, and in the second stage NbO2was simultaneously reduced and carburized to NbC. The first reduction occurred by a nucleation mechanism with an activation energy of 100 kJ mol−1. Independent experiments with NbO indicated that it was not involved in the reaction pathway. However, X-ray photoelectron spectroscopy revealed the presence of an oxycarbide phase which was probably the intermediate in the final transformation. Overall the reaction took place by the following steps:[formula]The oxycarbide phase transformed rapidly to the product NbC and was not observable as a bulk phase by XRD.