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In the field of echography, there is a large interest for the diagnostic potential of textures or speckle patterns encountered in echographic B-scan images. In this work, we present a new approach to this problem. We study the capability and the diagnostic value of a method to extract parameters describing tissue dynamics by tracking myocardial speckle pattern motion during the cardiac cycle. Such speckle motion is shown to be closely related to the myocardial tissue dynamics and therefore should be of diagnostic significance. A model was previously developed to generate typical B-scan images of the myocardium during the cardiac cycle. We appropriately modified the tissue parameters in our model to simulate the deformations happening during cardiac contraction (translation, wall thickening, fiber contraction, rotation etc.). The resulting simulated speckle pattern motion was then studied. An optical flow algorithm developed in our laboratory was successfully used to quantify this motion as a velocity field described by a set of linear equations. The correlation between this velocity field and the myocardial deformation was clearly established from the model for small deformation rates. In practice, the time interval between echographic frames (1/30 second) was expected to be adequate for only small tissue deformations to occur between frames; we could thus expect our method to be successful with real echocardiographic data. Clinical data studied with this procedure have indeed confirmed that velocity field could be obtained from myocardial speckle tracking; this allowed to characterize quantitatively the myocardial dynamics, in particular with respect to local wall thickening and myocardial contraction during the cardiac cycle. Those results indicate a potential for speckle tracking as a diagnostic tool to study myocardial deformation and contractility.