Many people have in one way or another contributed to the completion of this thesis.

First of all, I thank my supervisor Professor Jan Telgen for his excellent support and guidance throughout the past four years. Jan provided the right mix of expertise, experience, criticism, encouragement and challenges.

I am also grateful to Jan Buter. From the beginning of the project he has been an inexhaustible source of ideas, practical perspectives and ‘purchasing-enthusiasm’.

Next, I want to express my gratitude to the other members of the PhD committee. In particular I mention Professor Arjan Van Weele, Professor Freerk Lootsma and Professor Ulli Arnold for their comments and suggestions.

Furthermore, I thank the Dutch Association for Purchasing Management (NEVI) for sponsoring the research. Also, the involvement of Dr Albert Blom on behalf of the NEVI Research Foundation (NRS) is greatly appreciated.

This research could not have been completed without the co-operation of a number of companies and purchasing professionals. I thank Mr. Olde Agterhuis from Facility Services University of Twente, Mr. Heerink from the Central Military Hospital, Mr. Klingenberg from Honeywell Combustion Control Center and Mr. Heinen, Mr. Oostendorp and Mr. Smelt from Grolsche Bierbrouwerij for their participation in the experiments and the evaluation of the toolbox. Also, I express my gratitude to the municipality of Hengelo for giving me the opportunity to really experience and work within the practice of purchasing. Furthermore, I thank my fellow ISFAH-course participants for their interest in my research. The many discussions, meetings, company-visits and not in the least social programmes have absolutely contributed to my thinking and understanding of the purchasing practice. The assistance from Joost Holleman and Arjenne Louter in editing and structuring the thesis is also greatly appreciated. Jules Vos and Max Tropp are thanked for providing me with the Winchoice package, for their interest in the research and especially for the many discussions on decision making and multi-criteria decision support. I thank Rob van Stekelenborg (currently with KPMG) for our pleasant and constructive co-operation and for giving me the opportunity to participate in the project at Philips Medical Systems when he was conducting his PhD research at Eindhoven University of Technology.

I express my gratitude to my friends and (former) colleagues in the department of Technology and Management at the University of Twente. Each in their own way, they have helped me to complete this project.

Finally, I thank my family and friends for their continuous support and their patience while so many times I was so busy.

Luitzen de Boer,

Hengelo, August 1998.