The positive diagnosis of a sarcoidosis is often difficult since reliable laboratory and radiological parameters are not available. It is therefore often necessary to make the diagnosis with invasive methods. The Kveim skin test has many disadvantages, so that there have been many trials to facilitate the diagnosis by in vitro systems. With a modified and easy handable leucocyte migration technique in agarose (Clausen technique), 30 patients with certified sarcoidosis were tested. As controls served healthy volunteers and patients with various diseases such as Hodkins disease, Crohn's disease, tuberculosis etc. As antigene a Kveim suspension typ I was prepared according to Chase and was used in a concentration of 100 mug/ml. It could be shown, that leucocytes from patients with sarcoidosis demonstrated a significant inhibition of their migration in presence of Kveim antigene. Besides patients with Crohn's disease in no other group there was a migration inhibition. Therefore this in vitro system allows diagnostic differentiation and helps to find the diagnose which compares well to the results obtained with the Kveim skin test. Since the test is easy to perform and the results are available after 24 h the test is of diagnostic value for the clinical routine.