Myocardial tagging is a new noninvasive MRI method that allows the study of myocardial motion with high accuracy. However, with conventional tagging techniques tagging contrast is impaired at later heart phases due to longitudinal relaxation. An improved method, called Complementary SPAtial Modulation of Magnetization (CSPAMM), which separates the component of the magnetization with the tagging information from the relaxed component by subtraction of two measurements with first a positive and then a negative tagging grid, is presented. This technique improves the grid contrast and greatly facilitates the automatic evaluation of the myocardial motion. Thus the motion assessment of the entire heart cycle becomes possible. The improvements are documented by numerical simulations and by experiments on phantoms and on human volunteers.