Employing the concept of an incremental modulus, a model is nearing completion for the quantitation of stiffness-stress relations throughout the diastolic period. This model forms the basis for studying the importance of effects such as external constraints, muscle elasticity incomplete relaxation etc. in the determination of the diastolic pressure-volume relations following drug intervention and pacing induced angina. Clinical studies are being continued relative to the problem of predicting post-operative performance in valvular heart disease and in particular, the question of the relationship between diastolic and systolic function is to be addressed.