1965 Transactions of the Third International Vacuum Congress, Volume 1: Invited Papers is the first of two-volumes that review the state of knowledge in vacuum technology. The present volume comprises the opening address by Prof Auwárter and the twelve comprehensive main lectures. In keeping with the purpose of an international congress, the organizers took great pains to ensure that the choice of topics for the main lectures not only covered the scientific fundamentals as a whole, but also gave appropriate consideration to the technical applications. An analysis of the submitted topics shows that the strong points of research and development lie in the fields of ""Coating and Thin Layers"", ""Adsorption and Desorption,"" and ""Pressure Measurement and Leak Detection"". In the fields of application, ""Vacuum Metallurgy"" ranks highly. The papers published in the transactions originate from many European and overseas countries, proof that vacuum science is not only keenly pursued in all major industrial countries, but also that the new organizational form of the IUVSTA is capable of winning the services of all these countries for fruitful international cooperation in the vacuum field.