The use of gas-phase iodine and carbon dioxide as transport agents in the tantalum/carbon/tantalum carbide combustion synthesis system has been examined to determine the effects of transport agents on product composition and microstructure. Two tantalum reactant particle sizes, a range of transport agent concentrations, and total pressures were studied, The effects of the combustion conditions on product morphology and composition were evaluated using scanning electron microscopy, nitrogen adsorption (specific surface area), and X-ray diffraction analyses. The results of the investigation indicate that the presence of the iodine vapor and carbon dioxide significantly enhances the combustion synthesis process, leading to higher conversion efficiencies and influencing product microstructure. The results are discussed in the context of gas-phase and solid-phase transport models.