Existing studies of supplier involvement in new product development have mainly focused on project-related short-term processes and success factors. This study validates and extends an existing exploratory framework, which comprises both long-term strategic processes and short-term operational processes that are related to supplier involvement. The empirical validation is based on a multiple-case study of supplier collaborations at a manufacturer in the copier and printer industry. The analysis of eight cases of supplier involvement reveals that the results of supplier-manufacturer collaborations and the associated issues and problems can best be explained by the patterns in the extent to which the manufacturer manages supplier involvement in the short term and the long term. The results of this study reveal that the initial framework is helpful in understanding why certain collaborations are not effectively managed yet conclude that the existing analytical distinction among four different management areas does not sufficiently reflect empirical reality. This leads to the reconceptualization and further detailing of the framework. Instead of four managerial areas, this study proposes to distinguish between the strategic management arena and the operational management arena. The strategic management arena contains processes that together provide long-term, strategic direction and operational support for project teams adopting supplier involvement. These processes also contribute to building up a supplier base that can meet current and future technology and capability needs. The operational management arena contains processes that are aimed at planning, managing, and evaluating the actual collaborations in a specific development project. The results of this study suggest that success of involving suppliers in product development is reflected by the firm's ability to capture both short-and long-term benefits. If companies spend most of their time on operational management in development projects, they will fail to use the leverage effect of planning and preparing such involvement through strategic management activities. Also, they will not be sufficiently able to capture possible long-term technology and learning benefits that may spin off from individual projects. Long-term collaboration benefits can only be captured if a company can build long-term relationships with key suppliers, with which it builds learning routines and ensures that the capability sets of both parties are aligned and remain useful for future joint projects.

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Purchasing portfolio models have spawned considerable discussion in the literature. Many advantages and disadvantages have been put forward, revealing considerable divergence in opinion on the merits of portfolio models. This study addresses the question of whether or not the use of purchasing portfolio models is considered as a sign of purchasing sophistication. Using data from a broad sample of industries, it was found that purchasing sophistication is a two-dimensional construct: purchasing's professionalism and purchasing's position within companies. Results revealed that the position and the professionalism of purchasing are both positively related to the greater use of purchasing portfolio models. Findings indicate that portfolio usage is definitely a sign of purchasing sophistication.

SUMMARY Contrary to the growing number of academic publications on purchasing portfolio models in literature, little is known about their actual use. Kraljic's portfolio model, which was developed in 1983, seems to be the dominant approach in the profession. This model, however, does not provide guidelines for strategic movement of commodities and/or suppliers within the matrix. Based on an in‐depth case study, derived from a major Dutch chemical company, the use of portfolio techniques in purchasing has been explored and described. The results indicate that Kraljic's portfolio approach, when elaborated and tailored, indeed allows for sufficient guidance for developing effective purchasing and supplier strategies. The case study points out what supplier strategies are feasible and what conditions should be met in order to make them happen.