The original concept of diastolic function of the left ventricle was that the pressure within the left ventricle is determined by the balance between the forces due to pressures within the ventricular cavity that expand the ventricle and forces due to elasticity of the myocardium that resist this expansion. While this concept remains the centrepiece of our understanding of the diastolic pressure-volume relationship, it is now clear that several other factors play a role. During early diastole changes in the rate of active relaxation of the myocardium and so-called diastolic suction are important. During late diastole (and at end-diastole) the extent of relaxation, mechanical interaction between the ventricles modulated by the pericadium, and the pericardium itself are important (Fig. 1). Other factors — pulmonary-cardiac contact pressure, viscoelasticity of the myocardium, and engorgement of the coronary vasculature — are less important in determining the left ventricular diastolic pressure-volume relationship.