The indications for removal of fluid from the pericardial space fall into two categories: diagnostic and therapeutic. Most diagnostic pericardiocenteses occur in the context of chronic effusions, to assess for viral or bacterial infection, neoplasia, storage disease, or a connective tissue disorder. Therapeutic “taps” may be required in either elective or emergent circumstances. The former will include patients with recurrent, large-volume pericardial effusions, with a myriad of causes, including post-pericardiotomy syndrome, neoplasia, disorders of lymphatic drainage, and idiopathic effusions. Most of the emergent procedures are the result of misadventures in the catheterization lab or in hemodynamically compromised postoperative patients.