This thesis describes the development of a diagnostic tool to identify potential weaknesses in the interfaces between the key functions involved in new product development within manufacturing organisations. It comprises three parts: Part One introduces the field and reviews the literature. It discusses the subject of new product development (NPD), describes how the NPD process has evolved and outlines the key success factors which have been found to apply. It identifies and summarises the key issues which have influenced NPD and discusses the role that teams have had within the field. Key functions and their respective interfaces are identified and the barriers which exist between these functions assessed. A theoretical framework is presented which proposes that problems within these functional interfaces can be overcome by developing appropriate solutions based on accurate diagnosis of imbalance of functional perceptions within organisations. Associated research hypotheses and methodology for the research programme are also presented. Part Two describes the development and testing of a questionnaire to achieve this diagnosis. This details the identification of core issues through interviews in sample companies, initial testing of a questionnaire and the subsequent revision and retesting. Rationalisation of the questionnaire using both item and factor analysis techniques are then described and, following final testing, the use of these same techniques to develop a scoring system are also detailed. Part Three discusses the findings from the research programme and draws conclusions. The results obtained from the use of the diagnostic questionnaire within the participating organisations are compared with the literature and the development of the diagnostic questionnaire is evaluated. Finally the research hypotheses are examined and tested and conclusions relating to both the findings and the questionnaire development are drawn. Finally recommendations for the future use of the developed diagnostic tool are made.