Primary care research networks are fundamental to developing primary care-based research. A significant amount of their work is with locally organized projects. Working effectively with externally funded trials is another crucial way to inform the evidence base. There is little information on how trial teams may best work with multiple networks. We examined factors that might assist and impede collaboration between an externally funded trial and networks by exploring the systems networks used to assess externally approved trials. A large RCT was used as an example of an external trial. Networks were identified in areas where the trial could provide the intervention. Eighteen networks were sent standard letters asking for information about contacts and assessment procedures. We examined how long it took to identify a liaison person, what processes were used to assess the trial and how long these processes took. Sixteen of 18 networks (89%) agreed to work with the trial. Most networks provided initial information within a month of being contacted. There was no standard process for approving externally funded trials. The time taken to gain final approval varied from one week to three months. There is enthusiasm among networks to work with externally funded studies. It is feasible and can be successful, but current systems for approval are variable and often time-consuming. A defined turnaround time and central mechanism for approving trials could result in greater engagement of external trials with networks and an increased likelihood of a successful research.