The complex nature of new product development (NPD) activities within firms often requires high levels of integration between the Marketing function and the Research and Development (R&D) function. The nature of this cross-functional relationship has received considerable research attention with an emphasis on achieving successful departmental integration during NPD projects. This study examines the nature of cross-functional relationships (CFRs) from a micro-management perspective. That is from the perspective of the R&D Manager and the Marketing Manager, continues previous conceptual development by (Anon) that suggested that this working relationship is more complex than previously conceptualised by NPD researchers. By using data collected from 184 Australian NPD projects, this study provides empirical support for the proposition that interpersonal trust (affective and cognitive), interpersonal conflict (functional and dysfunctional) and interpersonal collaborative behaviour, do indeed have a strong association with new product project success.