Eighteen patients (3 men and 15 women; mean age 63 years) with right-sided tumors were evaluated by both transthoracic and transesophageal echocardiography from 1989 to 1996. The indications for echocardiographic studies included evaluation for a presumed mass and further evaluation of ventricular function and valvular function. Fifteen patients had right atrial tumors. These included 5 hypernephromas, 4 myxomas, 2 angiosarcomas, 1 lipoma, 1 cavernous hemangioma, 1 hepatoma, and 1 chondrosarcoma. Three patients had right ventricular (RV) tumors: 1 metastatic olfactory neuroblastoma, a leiomyosarcoma, a chondrosarcoma, and a fourth patient had infiltration of the RV free wall of unknown etiology. Biopsy of either right atrial or RV masses was performed with transesophageal echocardiographic guidance in 2 patients, and allowed histologic diagnosis before surgical resection. These findings indicate that tumors are more often found in the right atrium than in the right ventricle, and females predominate. Most tumors arising within the right atrium are benign, whereas those extending into the right atrium from outside are malignant. RV tumors are rarely encountered; when present, they are likely to be malignant.