In this study, two patterns of regional contract on of the left ventricle have been studied: endocardial motion and wall thickening, in order to check which of these was the most affected after myocardial infarction. The clinical relevance of this comparison was to assess which parameter of the regional contraction abnormality would best depict the severity of the infarction. Long axis cine-magnetic resonance slices were used to assess segmental systolic left ventricular endocardial motion and segmental systolic wall thickening in 39 normal subjects and in 30 patients at the chronic stage of an anterior myocardial infarction. In the group of normal subjects, endocardial motion and wall thickening showed significant regional heterogeneity. Overall endocardial motion was greater than overall wall thickening: 9.5 +/- 2.0 mm vs 7.1 +/- 1.8 mm. P = 4 x 10(-12) (3.1 +/- 1.2 mm vs 2.0 +/- 0.7 mm, P = 9 x 10(-5) after infarction). A significant linear correlation was found between these two parameters. In the infarction group, abnormality scores for endocardial motion and for wall thickening were calculated. These scores were defined as the average values exceeding the mean minus two standard deviations of the normal range for segments corresponding to the antero-septal-apical walls. The abnormality score for endocardial motion greater than the abnormality score for wall thickening: 0.31 +/- 0.12 vs 0.20 +/- 0.07, P = 9 x 10(-4). We conclude that, in clinical practice, endocardial motion is affected to a greater degree by myocardial infarction than is wall thickening and therefore constitutes a more discriminant index in the assessment of post-infarction patients.