A catheter for anchoring an electrode in a coronary sinus includes an elongate catheter body adapted to be inserted into a coronary sinus and at least one electrode on the catheter body. The elongate catheter body also includes at least one anchor movable between an undeployed configuration and a deployed configuration. When the anchor is in the undeployed configuration, the catheter may be introduced into and removed from the coronary sinus. When the anchor is in the deployed configuration, the anchor engages a tissue surface of the coronary sinus to inhibit movement between the catheter body and the coronary sinus, preferably without completely occluding the coronary sinus. The anchor may be a section of the catheter body having an expandable axial cross-section, an expandable member mounted on the catheter body, one or more wire anchors, or a flexible section of the catheter body.