Cine magnetic resonance imaging (cine MRI) was used to evaluate the cardiac structures and blood flow in congenital heart diseases with left-to-right shunts. Fifteen children with left-to-right shunts which were confirmed by echocardiography or angiography were investigated in the present study. Five children each had atrial septal defect, ventricular septal defect, and complete endocardial cushion defect. Their ages ranged from 4 months to 13 years (mean 5.5 years). Prior to cine MRI, the ECG-gated cardiac imaging using multi-slice acquisition was performed in all the children to localize the optimal slice for cine MRI. To select the optimal imaging planes for various cardiac structures, we used axial, coronal, sagittal and four-chamber views. Cine MRI was demonstrated by a fast low 30 degree flip angle imaging technique, with a 15 msec echo time, a 30-40 msec pulse repetition time, and a 256 x 256 or 128 x 128 acquisition matrix. Abnormalities of cardiac structures were defined extremely well in all the children using ECG-gated cardiac imaging. In 14 of the 15 children (93%), cine MRI clearly detected a left-to-right shunt flow, which was visualized as a low signal intensity area compared to the surrounding blood flow. Noninvasively, cine MRI provides accurate images of the anatomy of the cardiac structures, makes functional assessments of the cardiac chambers and walls, and flow relationships. It has no limitations of imaging planes imposed bones and lung, and is not associated with technical difficulties as required with echocardiography which has small cardiac window.(ABSTRACT TRUNCATED AT 250 WORDS)