It is known in the art to manufacture urethanes by reacting hydroxyl group-containing organic compounds, such as alcohols or phenols, with carbon monoxide and certain nitrogenous compounds, using metal carbonyls, certain metal complexes, and certain metallic compounds, as catalysts. Thus, British Pat. No. 1,080,094, to Ibbotson, teaches the above-described process using as a catalyst a mixture of two or more metal halides, at least one of the said metal halides being a halide of a transition metal; British Pat. No. 1,092,157, to Gamlen et al., teaches using as a catalyst a metal complex compound containing at least one transition metal and at least one unsaturated hydrocarbon ligand in which the unsaturated system forms a bond with the metal; British Pat. No. 1,087,896, to Ibbotson, teaches using as a catalyst a mixture of one or more metals capable of existence in two or more valency states and one or more halides of metals other than the metal or metals first mentioned and also capable of existence in two or more valency states; U.S. Pat. No. 3,338,956. to Mountfield, teaches using as catalyst, metal carbonyls. Applicant has discovered that the above reaction can produce very high yields of diurethane with relatively little undesirable side products if it is carried out in two stages, the first stage utilizing one temperature and pressure, and the second stage being carried out at a higher temperature and pressure.