THE serum protein levels in patients with periodontal diseases have been described by a number of workers. In the majority of cases, total protein was almost normal. Serum globulin, however, showed higher levels in patients, and albumin was lower (KARSHAN et al., 1952; MATSUMURA et al., 1960; TANIMOTO, 1960). SHANNON and GIBSON (1964) and SHANNON, TERRY and CHAUNCEY (1966) reported that there were no significant changes in serum albumin or globulin level in relation to periodontal status. Those experiments were performed in an attempt to reveal that some systemic or metabolic condition might operate as one of the contributing factors in periodontal diseases. Although they used salt-fractionation or electrophoretical methods to separate the serum protein fractions, they determined only two (albumin and globulin) or four (albumin, a-, /?and y-globulins). In the present investigation, the authors analyzed sera by immuno-electrophoresis on agar gel plates and obtained more detailed information. As controls, eight healthy men and three women aged between 18 and 30 years old were examined. Thirty patients aged between 18 and 60 years old were divided into three groups according to the roentgenographic examination and clinical signs, as follows: (1) Inflammatory type (Periodontitis): Inflammatory changes of gingiva and pocket formation are present. Mobility of teeth increased. Roentgenographically the type of alveolar bone resorption is horizontal. (2) Atrophic type (Periodontosis): Atrophy of the alveolar processes and gingival recession are the chief signs. Vertical bone resorption, pocket formation and increased mobility of teeth are present. (3) Mixed type: Gingiva recession with inflammation. Alveolar bone resorption is irregular. Each type was subdivided into three stages, namely, incipient, moderately advanced and far advanced. Serum GOT and GPT were determined in all subjects to eliminate liver dysfunctions. Patients with severe pus discharge from the gingivae were excluded. Serum protein fractions were separated by electrophoresis on cellulose acetate membrane (Sephadex, Joko Sangyo Co., Tokyo), using Verona1 buffer, pH 8 ‘6, ionic