A common problem during biopsy of the right ventricular septum using the flexible King's bioptome is the difficulty of accurately directing the tip of the long biopsy sheath against the septal surface. This can be important in that inadvertent biopsy of the more delicate ventricular free wall may lead to perforation and pericardial tamponade. An alternate method of sheath placement is presented. This involves the use of a No. 5 or 6 French balloon-tipped catheter within the long bioptome sheath in order to facilitate sheath passage and positioning. Catheter positioning is readily accomplished when documented by bioplane fluoroscopy, with alternate or additional two-dimensional echocardiographic position check as desired. Balloon-guided positioning for right ventricular septal biopsy appears to be a simple and safe technique that may be especially useful for relatively inexperienced operators and for patients with abnormal cardiac anatomy for whom endomyocardial biopsy (EMB) might normally be technically difficult.