Spontaneous cell mediated cytotoxicity (SCMC) and antibody‐dependent cell mediated cytotoxicity (ADCC) were examined in 25 patients with periodontal disease and a group of 25 age and sex matched control subjects. SCMC and ADCC were evaluated from the 51Cr activity released when peripheral blood lymphocytes were cultured with 51Cr labelled K562 and L929 cells, respectively. Four lymphocyte: target cell ratios were used, 50: 1, 25: 1, 12.5: 1, and 6.25: 1 in triplicate. There was no significant difference (p>0.05) in the SCMC and ADCC between the two groups. However, a very significant positive correlation (p < 0.001) was found between the degree of periodontal disease (Russell 1956) and SCMC.