21 healthy persons, 7 patients with chronic generalized periodontitis and 4 patients with chronic generalized gingivitis aged between 18 and 42 years were examined. Air from the oral cavity was collected with a special device; liquid samples were collected by washing the oral cavity with sterile water. Chemical compounds of the air and the washed liquid were analyzed by chromato-mass-spectrometry, gas-adsorption and gas-liquid chromatography. The content of dimethyl sulphide, dimethyl disulphide increased in the oral air and such volatile short chain fatty acids (VSCFA) as butyrate, propionate, acetate rose, but their aldehydes (butyraldehyde, acrolein, acetaldehyde decreased in oral fluid during periodontitis. The concentration of these compounds were found to be between the levels in control persons and during periodontitis. The content of pentane decreased in oral air. That depended on the intensity of inflammation and vessel disturbances. The results suggest that VSCFA produced by Porphyromonas, Prevotella, Fusobacterium and other periodontopathic bacteria, penetrate the oral mucosa and severely harm the periodontal tissue. The increase of dimethyl sulphide contributed to oral malodor during periodontal inflammation.