How do working relationships between functional managers develop, and how are they maintained? Does interpersonal trust drive communication, or is communication the building block of interpersonal trust? Massey and Dawes (2002) examined the causal ordering of three key behavioural constructs - communication behaviours, interpersonal trust, and interpersonal conflict in cross-functional relationships between Marketing Managers and Sales Managers. By using three competing models they found evidence that CFRs are built on a foundation of effective communication, specifically, bidirectional communication. This current paper is a replication of their study in the context of the Marketing/R&D relationship during 184 Australian new product development projects. It contributes to the literature, by corroborating the causal ordering suggested by Massey and Dawes (2002). These findings have significant implications for the selection of strategies by senior management to better integrate the Marketing and R&D functions.