Pericardial effusion (PE) in dogs most often is associated with neoplasia or idiopathic pericarditis, and frequently causes cardiac tamponade. Studies of PE in the cat are limited. Congestive heart failure (CHF) is the most common cause of PE in the cat. All cats diagnosed with PE on echocardiographic examination at the Matthew J. Ryan Veterinary Hospital of the University of Pennsylvania (MJR-VHUP) from 2000 to 2005. The clinical and pathologic findings in 146 cats with PE were reviewed. Records were examined retrospectively to identify additional underlying conditions. Follow-up status and cause of death were determined by review of the medical records or phone interviews with the owners. The most common cause of PE in this study was CHF (75%). Biochemical abnormalities were uncommon, but aspartate aminotransferase (AST) activity frequently was increased (85%). Follow-up information was available on 108 cats (74%). Median survival time (MST) was 144 days for cats that were not euthanized within 24 hours (n = 85). The MST of cats with heart failure was 41 days, whereas the MST of cats without heart failure was 361 days, when those euthanized within 24 hours were excluded. Survival time of cats with heart failure in this study was significantly shorter than previously reported, and significantly shorter than in cats without heart failure as a cause of PE.