SC RF Studies in Europe

The perspective to build large accelerators based on high gradient superconducting cavities posed a number of new problems that have been addressed in the preparation of the TESLA project. In this paper I mainly discuss the European contribution to the TESLA achievements and how they have been at the basis of the great impulse that the field is presently experiencing. Industrial production issues are focussed in terms of large scale production, reviewed quality control criteria and cost reduction.