The Trust in Construction project was a two-year EPSRC funded research into the impact of trust on construction project performance. Here we outline the development of the measurement tool used for assessing the level of trust in project team relationships, known as the Trust Inventory. We discuss the process and rationale for developing the Trust Inventory within the context of the study as a whole. The Trust Inventory was designed to support and integrate with a mixed methodology case study approach which looked at construction projects from a network perspective. By identifying key relationships in project teams and assessing the level of trust in those relationships, it would be possible to draw conclusions about the impact of trust in relationships on project performance.