Many studies in the product development literature discuss the benefits of partnering with suppliers. In these partnership relations buyers and suppliers establish long term, co-operative relationships during Product Development Projects (PDP) in order to reduce product development time and improve project performance. Traditional contractual approaches, on the other hand, where buyers work independently of suppliers and lack control over suppliers' resources, are commonly blamed for delays in the development time. This study constitutes of an initial effort to model and investigate these relationships analytically. The impact of scheduling strategies, the number of suppliers, and resource availability on PDP completion time is evaluated under contractual or partnership arrangement. Contractual relationships seem to provide a good or even better development times than the ones provided by the partnership approach. (C) 2001 Elsevier Science B.V. All rights reserved.