A process for producing Ni(CO).sub.4 from carbon monoxide and a source of nickel selected from the group consisting of elemental nickel, a nickel compound or mixtures thereof, provided the nickel compound is not nickel chloride per se or in admixture with a nickel carbonate ore, in an amount greater than 50% W/W nickel chloride; which process comprises (a) treating the nickel source with hydrogen at a pressure of at least atmospheric pressure and an effective temperature, in the presence of chloride anion or an in situ generator thereof precursor, to produce a resultant nickel; (b) reacting the carbon monoxide with the resultant nickel to produce the Ni(CO).sub.4; and collecting the Ni(CO).sub.4. The process offers the production of Ni(CO).sub.4 at atmospheric pressure and at a sufficiently high rate for direct use in subsequent deposition processes without the need for storage facilities.