Vanadium and molybdenum are recovered from spent petroleum PEMEX catalyst in the form of sodium vanadate and molybdate by leaching with aqueous NH3 or NaOH solutions after preliminary treatment of catalyst with CS2 or organic solvents. The use of recycled solvents allows the recovery of sulfur and avoids contamination of the atmosphere by considerable amounts of SO2. Different concentrations and operating conditions of NH3 and NaOH solutions are examined. It; is shown that; the use of these agents leads to yields from 88 to 92% of leached Mo and V in the form of compounds, allowing their further reutilization. These metals could be extracted selectively by the different; techniques applied, which represents an economic advantage for PEMEX.