The application of LIX 622 (oxime derivative) as an extraction reagent of molybdenum (VI) from sulfate media was studied. The extraction system was studied as a function of contact time, temperature, aqueous pH, diluent of the organic phase and metal and extractant concentrations. The extraction is exothermic and it is dependent on the organic diluent, aqueous pH and reagent concentration. The data have been analysed numerically to determine the stoichiometry of extracted species and their equilibrium constants. It was found that molybdenum was extracted into the organic phase by a complex mechanism which involves the formation of three species (MoO2L2, MoO4H3HL+HSO4-and MoO4H2HL, where L represents the extractant). Molybdenum stripping by acidic and ammonium hydroxide solutions was also studied.