Three-dimensional echocardiography is an emerging clinical method to assess cardiovascular disorders. The feasibility of using a linear mode scanning (parallel slicing) for transthoracic data acquisition has been demonstrated. In this study, we evaluated the feasibility of real-time transthoracic three-dimensional imaging of the heart using a fan-like scanning mode of echocardiographic data acquisition. We used a computer-driven motor to sequentially angulate transthoracic transducers over a fan-like arc up to 90 degrees. With careful ECG and respiratory gating, we acquired basic two-dimensional data set via parasternal and subcostal windows and performed dynamic three-dimensional reconstructions. The problems encountered included the need to repeat data acquisition sequences because of transducer movement or inappropriate gain and gray scale settings. From 15 scanning sequences in four patients, we were able to use ten sets of data. These yielded good quality three-dimensional studies projecting normal valves, a stenotic mitral valve, and an atrial septal defect, in a number of novel views. The valves could be visualized from above and from below as well as in other orientations, and the detailed anatomy appraised. Spatial relationships of the atrial septal defect with inferior and superior vena cava, coronary sinus, or tricuspid annulus could be uniquely displayed through views from the right side of the heart. This technique provided adequate new imaging planes not available from two-dimensional echocardiography. This experience demonstrates for the first time that transthoracic three-dimensional echocardiography using a fan-like scanning mode of data acquisition is feasible, and that it provides adequate visualization of intracardiac structures in unique projections.(ABSTRACT TRUNCATED AT 250 WORDS)