Over the last decade, research in the construction industry has explored the owner-contractor relationship in project management resulting in a different paradigm called partnering. Partnering is a relationship characterized by cooperation and collaboration in contrast to the adversarial relationship more commonly experienced between owners and contractors. This study utilized data collected from 276 construction projects to examine the stability in the owner-contractor relationship. Owner-contractor relationships were classified as being adversarial, guarded adversarial, informal partners, or project partners. Fifty-eight percent of the projects experienced some fundamental change in working relationshipeither positive or negative. Projects that began as formal partnerships were the most stable with over two thirds ending as they began. Guarded adversarial was the least stable with fewer than 30% maintaining this kind of relationship at the end of the project. Content analysis of the reasons stated for the change revealed factors that contribute to an improvement or deterioration in working relationships. The writers use this analysis to make recommendations for sustaining and improving partnerships between owner and contractors.