OBJECTIVE--Right ventricular regional contractility has been thought to be difficult to assess precisely. Cine magnetic resonance imaging with presaturation myocardial tagging was employed to quantitate the contraction of the right ventricular free wall and to identify normal performance compared with the left ventricle. METHODS--Nine normal volunteers, aged 27-39 years, were examined in a 1.5 Tesla superconductive magnet, and short axis and four-chamber sections at the mid-ventricular level were imaged with cine magnetic resonance sequences. Tags, applied at end diastole as two parallel black lines, intersected the mid-portion of the free wall, dividing it into upper, centre, and lower segments in the short axis section, and anterior, middle, and posterior segments in the four-chamber section. From a series of cine magnetic resonance images at 50 ms intervals over a cardiac cycle, end diastolic, and early, mid-, and end systolic images were chosen for calculation of the endocardial, epicardial, and mean percent fractional shortening (%FS) in the six segments. RESULTS--There was (1) a gradual increase in %FS in systole in both sections (P < 0.001, < 0.005); (2) a poor transmural gradient of contractility; (3) a predominance of meridional shortening (whole length, mean end systolic %FS (SD): short axis, 17.4 (3.1)%; four-chamber, 30.1 (4.1)%; P < 0.001) in contrast to dominant circumferential shortening in the left ventricular lateral wall; (4) lower predominance of contractility in the short axis section (P < 0.001), and a middle dip of contractility in the four-chamber section (P < 0.005). CONCLUSIONS--Heterogeneity of contractility was closely correlated with the myocardial fibre architecture, and with wall stress determined by its thickness and curvature. It was proved that right ventricular regional function could be analysed non-invasively using cine magnetic resonance imaging with myocardial tagging.