1. IN A PROCESS FOR MANUFACTURING A CATALYST CONSISTING ESSENTIALLY OF AN ALUMINA CARRIER HAVING A SPECIFIC SURFACE OF 120-500 M2/G. AND A PORE VOLUME OF 0.2-0.9 CC./G. NICKEL SULFIDE OR COBALT SULFIDE, AND A SULFIDE OF A GROUP VIA METAL, SAID SULFIDES BEING PRESENT IN A CATALYTIC AMOUNTS, WHICH PROCESS COMPRISES IMPREGNATING THE ALUMINA CARRIER WITH A SOLUTION OF COMPOUNDS OF SAID METALS WHICH FORM METALLIC OXIDES UPON CALCINING; CALCINING THE IMPREGNATED CARRIER; AND SULFIDING RESULTANT CALCINED CATALYST WITH A GAS CONTAINING HYDROGEN SULFIDE, THE IMPROVEMENT IN SAID IMPREGNATING AND CALCINING STEPS OF: (1) IMPREGNATING SAID CATALYST WITH A SOLUTION CONSISTING ESSENTIALLY OF A NICKEL OR COBALT COMPOUND CAPABLE OF FORMING AN OXIDE UPON CALCINING, DRYING AND THEN CALCINING THE IMPREGNATED PRODUCT IN THE PRESENCE OF AIR AT 700-850*C.; AND (2) IMPREGNATING RESULTANT CALCINED PRODUCT FROM STEP (1) WITH A SOLUTION CONSISTING ESSENTIALLY OF CATALYTIC QUANTITIES OF (A) A NICKEL OF COBALT COMPOUND CAPBALE OF FORMING AN OXIDE UPON CALCINING AND (B) A COMPOUND OF A GROUP VIA METAL CAPABLE OF FORMING AN OXIDE UPON CALCINING, DRYING AND THEN CALCINING THE RESULTANT IMPREGNATED PRODUCT IN AIR AT 400-600*C.; THE AMOUNT OF NICKEL OR COBALT OXIDE INCORPORATED IN THE CARRIER IN THE FIRST STEP BEING SUFFICIENT TO IMPROVE THE STABILITY OF THE CATALYST SO THAT THE COMBINATION OF STEPS (1) AND (2) YIELDS A CATALYST HAVING A HIGHER STABILITY DURING HYDROGENATION OF DIOLEFINS THAN A CORRESPONDING CATALYST PREPARED WITHOUT THE FIRST HIGH TEMPERATURE CALCINING STEP.