The invention relates to a catalytic high-pressure process for the CO2 reforming of hydrocarbons, preferably methane, in the presence of iridium-comprising active compositions and also a preferred active composition in which Ir is present in finely dispersed form on zirconium dioxide-comprising support material. The predominant proportion of the zirconium dioxide preferably has a cubic and/or tetragonal structure and the zirconium dioxide is more preferably stabilized by means of at least one doping element. In the process of the invention, reforming gas is brought into contact at a pressure of greater than 5 bar, preferably greater than 10 bar and more preferably greater than 20 bar, and a temperature which is in the range from 600 to 1200° C., preferably in the range from 850 to 1100° C. and in particular in the range from 850 to 950° C., and converted into synthesis gas. The process of the invention is carried out using a reforming gas which comprises only small amounts of water vapor or is completely free of water vapor. In the process, the formation of carbonaceous material on the catalyst is greatly suppressed while carrying out the process, as a result of which the process can be carried out over a long period of time without significant decreases in activity occurring.