The present study was undertaken in order to determine the possible alterations in whole saliva and the periodontal status in patients with diabetes mellitus (DM), and was conducted on 17 patients with DM and 17 systemically and periodontally healthy subjects. When the subjects were evaluated clinically, significantly increased probing depths were noticed in the DM group when compared with the healthy subjects. In whole saliva samples, sodium, potassium, total protein, amylase, thiocyanate, and secretary IgA levels were determined in both groups. Difference between the two groups regarding the mean salivary potassium levels were found to be statistically significant since the mean salivary potassium levels in the DM and the control groups were 2.470+/-9.04 mmol/L and 14.30+/-3.88 mmol/L, respectively. The mean salivary total protein, amylase and secretary IgA levels in the DM group were 2.41+/-1.0 mg/mL, 124.2+/-79.7 U/mL and 6.86+/-3.50 mg/L, all being significantly higher than the control group. However, no significant differences could be shown for the salivary sodium and thiocyanate levels. Nor was there any difference between nan-insulin dependent diabetes mellitus (NIDDM) and insulin-dependent diabetes mellitus (IDDM). The findings of the present study suggest that, besides the clinical examinations, the determination of the possible alterations in the composition of whole saliva might also be helpful in understanding the increased severity of periodontal disease in diabetic patients.