There is increasing evidence that the alterations of function and/or level of adhesion molecules play a key role in the pathogenesis of autoimmune diseases, such as Graves' disease or type 1 diabetes. The aim of the present study was to evaluate the expression of lymphocyte function-associated antigen 1 alpha (LFA-1 alpha, CD11a) and L-selectin (CD62L) molecules on peripheral mononuclear cells in Graves disease and type 1 diabetes in comparison to healthy controls, since they were shown to play an important role in lymphocytes and/or monocytes migration into the organs affected by immune process and are suggested to contribute to the pathogenesis of Graves disease and type 1 diabetes. The percentages of monocytes/lymphocytes expressing LFA-1 alpha antigen and lymphocytes expressing L-selectin antigen and the fluorescence intensity of the studied molecules were measured by flow cytometry. At the onset of both autoimmune diseases the percentage of highly CD11a positive lymphocytes and the mean fluorescence intensity were statistically higher than in the healthy controls and patients with Graves' disease after thyreostatic therapy. The fluorescence intensity of LFA-1 alpha on monocytes was also increased in type 1 diabetic patients, but not in Graves' disease. The analysis of CD62L antigen expression on peripheral blood lymphocytes revealed decreased percentages of L-selectin positive cells in patients with Graves' disease (before and after treatment) and insulin-dependent diabetes in comparison to the controls. Our study suggests that the alterations of the expression of CD11a and/or CD62L molecules on peripheral blood lymphocytes could be the markers of ongoing autoimmune process in Graves disease and type 1 diabetes.