Diabetes mellitus is not just a simple metabolic disorder, however, it is considered to be a cardiovascular disease of a metabolic origin. This is apparent especially when speaking about type 2 diabetes (DM II). The objective of our study was to determine whether a comprehensive spa treatment (procedures and drinking cure) may affect the level of the sympathetic tone of patients suffering from DM II. As an indicator of the sympathetic tone, selected electrocardiographic parameters derived from the heart rate variability and microwave alternans were chosen. There were 96 patients enrolled in our study: 38 patients with poorly controlled DM II and two control groups: 9 patients with compensated DM II and 49 patients, average age without diabetes or other disorders of the glucose metabolism. All received an identical spa treatment and continued their medical therapy. The electrophysiological examination of patients was performed before and after a three-week spa treatment using the KARDiVAR system. Parameters derived from the analysis of heart rate variability (HRV), microvolt T-wave alternans, and microvolt R-wave alternans were analyzed in order to evaluate the tones of the autonomic nervous system (ANS). The control group showed a slight increase of parameter the index of activity of regulatory systems (IRSA) (4.4+/-1.3 vs. 3.8+/-1.4; p=0.006) after the spa treatment, while increased heart rate (80.9+/-11.0 vs. 74.6+/-9.6; p=0.028), reduced index of centralization (IC) (1.3+/-0.6 vs. 2.9+/-1.4; p=0.027) and reduced index of myocardium (IM) (9.9+/-7.4 vs. 18.0+/-6.3; p=0.041) were found in patients with a compensated DM II. Patients with a poorly compensated DM II showed a decreased IM (10.9+/-8.6 vs. 16.9+/-5.2; p=0.001) and also a reduced IRSA (4.1+/-3.5 vs. 6.3+/-1.9; p=0.001). The results proved favorable changes in ANS cardiovascular control of patients with DM II after a spa treatment, especially in terms of reducing the sympathoadrenal system activity (decreased IRSA), improving electrical stability of the myocardium and increasing centrally controlled heart rate variability without overloading the cardiovascular system (drop of IM).