The components of green tea extracts such as catechins and polyphenols gain increasing significance in tumor research and immunology. - The clinical double blind study presented here was aimed at the investigation on how green tea catechins and polyphenols in the form of green tea dragées may influence the inflammatory behaviour of the gingiva. A total of 47 test persons with a mean age of 25.76 years (23 males, 24 females) were randomly divided into two groups: one group (n = 22: 11 males, 11 females) received chew candies containing green tea extracts, the other group (n = 25: 12 males, 13 females) received placebos with the same flavour but without active substances. At the beginning of the four week investigation period, a professional dental cleaning was carried out on all test persons. Then the persons were instructed to do their usual dental cleaning and chew eight candies distributed over the day. The API (approximal plaque index) and the SBI (sulcus bleeding index) were determined after seven days (API-1, SBI-1) and after another 21 days (API-2, SBI-2). Within the verum group, a mean value of 33.2% +/- 18.3% was determined for API-1, and 29.6% +/- 17.5% for API-2. The mean SBI-1 was 5.9% +/- 7.6%, and 3.6% +/- 5.8% for SBI-2. The clinical data within the placebo group were different: The plaque index values changed from API-1 30.3% +/- 16.3% after one week to API-2 31.8% +/- 17.2% after another three weeks. The values for the inflammatory degree of the gingiva had also changed to the negative: from SBI-1 3.4% +/- 4.1% after seven days to SBI-2 4.7% +/- 6.4% after another 21 days. Whereas in the verum group a distinct improvement in both API and SBI values could be stated, slight worsening of the values were determined for the placebo group. The results indicate that the oral application of green tea catechins and polyphenols might have a positive influence on the inflammatory reaction of periodontal structures.