Abstract: Methods for treating bodily tissues and fluid vessels are disclosed. According to a method of repairing a perforation in a bodily fluid vessel, a viscous, moldable substance is inserted into the vessel at the location of the perforation. A path is opened through the moldable substance to permit fluid flow through the vessel. According to a method of introducing a tissue-killing substance into a bodily fluid vessel, a catheter is provided that has a blocking mechanism configured to selectively block and unblock the vessel. The catheter also has a delivery system that is configured to introduce the tissue-killing substance into the vessel. The vessel is substantially blocked upstream of a selected tissue using the blocking mechanism. The tissue-killing substance is introduced into the vessel through the delivery system, and the vessel is unblocked when the tissue-killing substance has substantially traveled toward the selected tissue.