Transesophageal echocardiography in the adult uses a relatively large diameter probe, which may be poorly tolerated by certain patients. The use of a smaller probe designed for pediatric patients was studied in 50 adults (21 males and 29 females), and concomitant transesophageal echocardiography studies were performed using the regular adult-sized probe in 28 of these patients. The smaller pediatric transesophageal echocardiography probe was easier to pass, better tolerated, caused a smaller heart rate increase (13 +/- 3 vs 20 +/- 4 beats/min, P = 0.0029), and required no sedation in more patients than the adult transducer. The resolution of the two-dimensional and color Doppler images in the mid and near fields of the smaller probe were comparable to the larger probe, as were the maximal area of mitral regurgitation and the ratio of the maximal proximal width of the aortic insufficiency jet to the left ventricular outflow tract diameter in patients with these lesions. However, the image resolution was noticeably inferior to the adult probe in the far field, such as when imaging the distal left ventricle or imaging structures transgastrically. Therefore, the smaller probe designed for pediatric use allows satisfactory near- and mid-field two-dimensional and color Doppler flow imaging in comparison to the adult probe and would be expected to be beneficial in adult patients in whom superior quality imaging of the far-field is not required clinically, those who tolerate poorly the adult probe, relatively high-risk patients in whom no sedation is desirable, and in those patients in whom passage of the larger probe is unsuccessful.