The periodontitis is an inflammatory disease condition caused by a variety of oral microorganisms. A hyper reactive host response regulation is triggering the disease progression in a small part of the world wide population – around 10% at most – resulting either in a local or generalized aggressive form of manifestation. Bleeding is a final act in a process of tissue and capillary damage initiated by bacterial presence and modulated by pro-inflammatory cytokines. Calibrated assignment of bleeding intensity as a parameter for the severity of the disease is considered golden standard for diagnosing gingivitis – an inflammatory condition restricted to the soft tissues. Periodontal inflammation regularly causes attachment loss and is accompanied by loss of alveolar bone and a phenomenon named “pocketing”. The severity of this disease condition is currently characterized by assessing either the probing pocket depths (PPD) or the attachment loss (AL). The evaluation of bleeding tendency as Bleeding on Probing (BoP) is currently an additional dichotomous finding. The aim of the present study was to assess the suitability of a visual calibration of a Pocket Bleeding Index (PoB-Index) to reflect the real inflammatory status of each single probed periodontal pocket. By matching single grades of the index suggested – i.e. the single visually assigned bleeding grades - with parameters such as bleeding duration (stop watch) and amount of blood sampled by capillary tube correlation coefficients were calculated. Correlations between PoB-Index and the probing depth and PoBI and the amount of gingival crevicular fluid (GCF) sampled as exudates that follow a gradient were calculated also to objectify the visual calibration of bleeding intensity. The capillary dilatation is initiated as first step in a cascade of inflammatory reactions in front of all clinical signs and results in a measurable increase of the GCF. Since periodontitis progresses episodically, i.e. phases of activity are followed by phases of inactivity the capillary dilatation follows the same pattern. The mean age of 17 participating patients recruited was 32 years; 10 of them were non-smokers whereas 7 were smoking. All patients enrolled did not have any periodontitis therapy or received any antibiotics prescribed for the last 12 months. All patients underwent intensive instructions in oral hygiene repeatedly, thus the allocated plaque index remained for the duration of the study < 25% (API < 25%). After completion of instrumentation (S/RP) all patients received Amoxicillin (500 mg) and Metronidazol (250 mg) x 3 daily for 10 days per os prescribed. The assessment of the study parameters was carried out at baseline after completion of the initial therapy (before S/RP), at month 3, 6 and 9 past active therapy. In total 575 sites were evaluated and monitored. For improving the reproducibility, all measurements were undertaken under equal conditions in all patients. The statistically significant correlation between the GCF amount and the PoB-Index grades at baseline… Advisors/Committee Members: [email protected] (contact), w (gender), Prof. Dr. A. Friedmann (firstReferee), Prof. Dr. T. Kocher (furtherReferee).