The Doctoral Thesis builds and tests a theoretical model that evaluates the contribution of shared knowledge and information technology to manufacturing performance. This is achieved through a sectorial research study among Manufacturing, Quality and R&D groups in the global economy era of the 21st century.

Theoretically, our research stands uponthe 'knowledge-based theory of the firm'. The theory has received influences from earlier research lines. It is considered to originate from the 'epistemology' of the cognitive philosophers and -through contradiction to the 'transaction cost economics' and the traditional product-based or competitive advantage view-it builds heavily upon the 'resource-based theory'. Starting with an analysis of previous empirical studies and by means of a productive synthesis, we develop the Shared Knowle! dge and Information Technology evaluation model which we later use in order to test the investigation hypotheses. Survey data collected from 51 medium to large sizeindustrial companies with a total of 112 manufacturing groups, representing 5 industrial sectors (alimentation, automotive, chemical and pharmaceutical, electro-mechanical,and textile) were analyzed to test the model.

A methodology, particularly deployed for the Thesis and the proposed evaluation model, was developed. Its key elements are:

(a) Two types of questionnaires, addressing the inter-group relationships andthe performance issues respectively, were developed and pilot tested prior to being used as the principal researchinstruments.

(b) Design of the indicators and measures has been carried out using two types of measures, general and multiplicative, for all the variables. Manufacturing group performance has been conceptualized in two parts: operational and service performance.

(c) Key-informant methodology has been used for selecting ourresearch responders.

(d) Validity threats have been given special attention and three different types of validity criteria are applied.

(e) Path analysis, a regression-based technique that permits testing of causal models, has been used. The investigation hypotheses have been tested and found to be fully or partially supported, by the significance -or insignificance- of the relevant paths.

(f) Finally, four confirmatory tests have been conducted in order to further secure the validity of the hypotheses.

As shared knowledge and information technology (IT) are central points of our investigation, we have focused on the issues of Knowledge Management (KM), and we have purposely directed our research on specific IT Systems for Supporting Collaboration and Knowledge-based Work. Our final target was to connect both shared knowledge and information technology to manufacturing performance, the subject matter of our investigation. Today's global economy era is the environment of our study, so it was under this perspective als! o that: (a) we have examined theinfluences of the globalization phenomenon to the recent information technology developments; (b) we have regarded KM and sharing knowledge in practice as an answer to globalization.

Finally, our conclusions are presented together with a reference to the study's limitations and some recommendations for future research. Based on the literature and the results of our research we are demonstrating that the two main findings of the study -the proved significant contributions of (a) shared knowledge to the manufacturing group performance, and (b) information technology to, mainly, the manufacturing group performance and, secondarily, to sharing knowledge- are useful to researchers and the business community alike. Manufacturing, Quality and R&D groups have the opportunity to increase shared knowledge and, in this manner, to positively affect manufacturing performance by developing mutual trust and influence through repeated periods of positive face-to-face or IT-based communication, social interaction and common goal accomplishment.