Summary:Collaborative networks of doctors to conduct joint clinical studies in the greater area of Leipzig were set up in early 1998 involving 28 rheumatologists, 67 orthopaedic surgeons, 10 oncologists and 197 general practitioners (GPs). Private doctors refer their patients solely for possible inclusion in clinical studies. Their main task is selection of patients, that also includes an explanation of the study and assessment of the motivation of their patients. The clinical studies are carried out at the Clinical Study Centre: “Centre for Therapeutic Studies” (Zentrum für Therapiestudien, ZET e.V.). In two large scale studies in rheumatoid arthritis and osteoarthrosis, respectively, the ZET e.V. ranked in the top three centres with regard to recruitment of suitable patients amongst more than 100 centres internationally. Results of an audit by the international quality assurance department of the sponsor revealed no GCP relevant findings. In conclusion, the principle of collaborative networks with private doctors may open new avenues for doing clinical research in Germany.