The reactivity of the aliphatic dicarboxylic acids (DCAs) mixtures in conditions similar to industrial wet air oxidation (WAO) process conditions has been investigated. DCAs have potential to be separated during WAO of highly polymerized organic matter (e.g., organic waste, biomass, kerogen in oil shale) before transforming to final oxidation products (CO2 and water). However, a shortage of information about the DCAs stability in such processes restricts this application. The influence of oxygen pressure, temperature, pH, various metal salts, and radical generating organic compounds on DCAs possible transformation was established. High stability of DCAs (C-4-C-10) was shown at 175 degrees C with 40 bar of oxygen mixture in wide pH range. The increase in the DCA decomposition with the formation of lower chain DCAs was found to be inevitable in the presence of alkali and homogeneous iron or copper salts in nonbuffered solutions. The relationship between organic co-oxidants, such as malonic acid and resorcinols, and the stability of DCAs was studied. Of them, 5-methylresorcinol was the most efficacious in