Circulating immune complexes were estimated in the sera of 50 patients with Type II or non-insulin-dependent diabetes mellitus (NIDDM) and 50 nondiabetic patients with periodontitis. The values were compared with that of 50 age- and sex-matched controls. There was a significant rise in circulating immune complexes (CIC) in both the groups of patients compared to controls. The levels of CIC were significantly higher in diabetic patients with periodontitis compared to nondiabetics. The study shows that the circulating immune complexes may have a role in the pathogenesis of periodontal disease in diabetic patients.