abstract—The rate of migration of leukocytes (OMR) was estimated by counts of sequential mouthrinses in 81 human subjects in order to evaluate its usefulness as a laboratory test of oral inflammation. Periodontitis was taken as a model, and neither patients nor controls had any other oral inflammation. Patients with advanced periodontitis, but with periodontal destruction of about the same level, were divided into two groups, acute phase and chronic phase. The mean number of leukocytes entering the oral cavity in 30 s was estimated in these two groups. In the same patients the difference between the cell count in the first rinse and the OMR level was estimated, to test whether it could be taken to indicate the grade of acuteness of the inflammation (GAI). OMR and GAI were assessed in the patients with periodontitts after the initial treatment and at Follow‐up 1 year after completion of the full treatment, which almost always included surgical procedures. The results indicate that the OMR reflects the existence of oral inflammation and can be used as a laboratory test with the same reservations as white blood cell counts for systemic inflammation. The difference in GAI between patients in the acute and chronic phases of the disease was highly significant, indicating that this test gives information about the severity of the inflammat