The study was carried out on 31 diabetic patients of both sexes hospitalised in the Clinical Hospital of Diabetes and Nutritional Diseases "Dr. I. Cantacuzino". They were divided in 2 groups: patients with insulin-dependent diabetes (IDDM) and noninsulin-dependent diabetes (NIDDM) and compared with a group of control non-diabetic subjects. Total mixed saliva was sampled in the morning (07:30-08:00) and in the afternoon (17:30-18:00) without stimulation and tested for amylase activity, proteins and density. The study revealed that the density and the amylase activity have the same diurnal behaviour for the diabetic patients and healthy control subjects either. The only difference was the amplitude of maximal activity (in the morning for density and in the afternoon for the amylase activity). Salivary proteins have a similar diurnal behaviour for both diabetic groups (maximal values in the morning and minimal values in the afternoon) in contrast to healthy control subjects that presented less obvious diurnal changes.