Aim      To study intracardiac hemodynamics in healthy men in supine and prone positions.Material and methods  This echocardiography study included 14 apparently healthy men at a mean age of 38 years.Results In a prone position, the heart configuration and location in the chest changed, the heart rate increased by 7.3 %, and the transaortic flow velocity decreased by 13.7 %. Also, early and late right ventricular diastolic filling velocities and the pulmonary artery flow velocity were increased by 31.7, 11.4, and 5.6 %, respectively. In the intact tricuspid valve, the velocity and regurgitation pressure gradient were reduced by 7 % and 14.2 %, respectively.Conclusion      In a prone position, spatial changes in the location of the heart and its structures influence velocities of intracardiac blood flow, which may initiate the development of heart failure if the prone position is long-lasting.