Cytopathology diagnosis of three hundred and thirty three pericardial effusions performed between September 1999 and August 2006 were systematically analyzed and compared with the biopsy in 71 cases. We described the clinical circumstances, the etiologies, the cytomorphologic features of the effusions, the role of liquid based cytology and ancillary studies such as immunocytochemistry and the sensitivity of cytopathology compared with histopathology. Among the 57 pericardial tumors, 51 (89%) were metastatic carcinomas--included 42 (73%) adenocarcinomas--, 5 (9%) were malignant lymphomas and one (2%) was a malignant mesothelioma. Cytology of pericardial effusion with ancillary studies enables rapid cytodiagnosis as specific as histodiagnosis provided by biopsy.