Background: Hypereosinophilic syndrome (HES) is a peripheral eosinophilia characterized by elevated absolute eosinophil cell count (>1.500 cells/\muL) and consequent tissue and end-organ damage. Our aim was to evaluate the mitral annular (MA) and/or tricuspid annular (TA) parameters of patients with HES and to determine whether there are any changes in these parameters compared to healthy individuals. Methods: 17 patients with HES were involved in our study, 2 cases were excluded due to suboptimal image quality (mean age of the evaluated patients: 61.7 \pm 11.2 years, 10 males). Their data were compared with those of 24 healthy subjects (mean age: 55.2 \pm 7.9 years, 12 males) in the control group. Complete echocardiographic examinations were performed including two-dimensional (2D) Doppler echocardiography and three-dimensional echocardiography (3DE) to assess the MA and the TA. Results: Comparing the echocardiographic parameters of the HES patients with those of the healthy volunteers, the following changes were seen: the interventricular septum was significantly thickened in HES patients, no other significant changes were detected between the examined patient groups. End-diastolic and end-systolic MA diameters, areas and perimeters were increased and MA fractional area change and MA fractional shortening were decreased in HES patients. From TA morphological parameters, only end-diastolic TA area and end-systolic TA perimeter were significantly increased in HES patients. Functional TA parameters showed no significant alterations in the HES group. In patients with HES, no correlations could be detected between 2D and 3D echocardiographic data with the examined laboratory findings. Conclusions: The extent of the dilation of the MA is more pronounced than that of the TA in HES. MA functional impairment is present in HES.