The term "Vacuum Metallurgy" and the diverse pressure ranges appli- cable to the vacuum technique are being explained. With the aid of some examples, the physico-chemical principles of the metal-gas systems are in- vestigated and the influence of the points of equilibrium due to reduction of pressure is described; simultaneaus deoxidation and decarbonisation during formation of CO can also be promoted through pressure reduction. The Van- Arkel-De-Boer process as weil as the extraction of aluminium by way of aluminium subchloride are special reduced pressure methods. The more recent technique in the field of vacuum metallurgy is shown by means of numerous examples, furnaces for induction, electric-arc and elec- tron beam melting are being dealt with. Of the metal extraction processes, the thermal magnesium extraction, ferrochrome decarbonisation and raw lead dezincking in vacuum are described. Resurne L'expose commente le terme ainsi que les diverses phases de pression dans la technique du vide. A l'aide de quelques exemples, l'auteur explique les bases physico-chimiques de systemes metallo-gazeux et l'influence exercee par l'abaissement de la pression sur les conditions d'equi- libre des corps. La desoxydation et la decarburation simultanees des metaux, en faisant appel a la formation de CO, peuvent se realiser de preference par depression. Les procedes speciaux d'application du vide sont entre autres le procede Van-Arkel-De-Boer et la production de l'aluminium en partant du sous-chlorure d'aluminium.