Abstract The kinetics and practical aspects of the applicability of a new uranium leaching method — the HSS (H 2O 2Na 2SO 4H 2SO 4) system — in the extraction of uranium from a typical New Mexico ore was investigated in the temperature range 30–80°C and at constant pH of 4.0–6.0 ± 0.1. The effect of Na 2SO 4 and H 2O 2 concentrations, pH, temperature and Fe 2+ addition on the rate and degree of uranium extraction was quantitatively established. Based on the nature of rate dependence on the H 2O 2 and Na 2SO 4 concentrations, an oxidation reaction mechanism involving sulfated Fe 3+ species and H 2O 2, including its decomposition products (O 2 and HO 0 radicals) has been suggested to account for the dissolution of tetravalent uranium compounds. In order to ascertain the applicability of the HSS process to other uranium ores, a comparative study was made on two other US sandstone ores. The results of this study indicated that the ores responded to the leaching tests differently. On the basis of this experimental study, a generalized flow-sheet of the HSS process has been proposed.