This volume contains the papers from the 4th IFAC conference on Fieldbus Systems and Their Applications (FeT'2001) held in Nancy, France, 15 - 16 November 2001. This conference was, for the first time, sponsored by IFAC with previous conferences being held in Vienna (Austria) 1995, 1997 and Magdeburg (Germany) 1999. The conference was supported by IFAC, the technical committees on Components and Instruments, on Advanced Manufacturing Technology, on Real-Time Software Engineering and their chairmen. The program covered a variety of research topics, which are of current interest, such as: -performances, -dependability of fieldbus based systems, -definition of devices profiles and architectures problems, -conformance testing and interoperability, -scheduling, -new technologies and wireless systems. More and more papers related to the validation and to the evaluation of application, using formal methods and techniques. These papers came from academic and industrial authors from many countries and the diversity of the points of view expressed led to an interesting conference, rich in debates. Many papers relate to the validation and evaluation of applications, using formal methods and techniques. These papers come from academic and industrial authors in many countries, and the diversity of the points of view expressed leads to an interesting and lively proceedings.

Four plenary papers, written by well-known specialists, provide tutorial material, as well as some history and background, and introduce the more specialised content which follows. Altogether nearly 50 papers are presented.