BACKGROUND AND OBJECTIVES: Since echocardiography became a routine diagnostic tool, pericardial effusion has become a common clinical finding. The major causes of hemorrhagic pericardial effusion are malignancy and tuberculosis. However, it was unknown to the use of biochemical analysis of pericardial fluid and serum, for differentiation of malignancy from tuberculosis. To evaluate this, we investigated the biochemical analysis of pericardial fluid and serum in relation to the causes of pericardial tamponade. SUBJECTS AND METHODS: 46 patients who were admitted to Pusan National University Hospital from January 1, 1995, to April 30, 2002, and underwent both a pericardiocentesis and a pericardiostomy for the relif of cardiac tamponade, were included in this study. the pericardial fluid was routinely analyzed for the following: gross appearance, cell count, glucose, total protein(P), lactate dehydrogenase(LDH), cytology, gram stain, cultures for bacteria and mycobacterium, pericardial fluid to serum ratios of total protein and lactate dehydrogenase,(p/s TP, p/s LDH, respectively). RESULTS: f the 46 patients who underwent both pericardiocentesis and pericardiostomy, for the relief of cardiac tamponade, 33 patients(71.7%) had hemorrhagic pericardial effusion. The common causes of hemorrhagic pericardial effusion were malignancy(51.5%) and tuberculosis(33.3%) but, those of nonhemorrhagic pericardial effusion were idiopathic (38.5%). Cell counts were higher in hemorrhagic than nonhemorrhagic group(p=.029). Serum LDH(sLDH) was higher in malignant than tuberculous group(p=.001) but, serum total protein(sTP) was higher in tuberculous group(p=.004). Compared malignant group with tuberculosis group in patients with hemorrhagic pericardial effusion, p/s ratio of LDH and sTP were higher in tuberculous group (p=.029, p=.017), but sLDH was higher in malignant group(p=0.002). CONCLUSION: It is difficult to differentiate tuberculosis from malignancy only on the basis of the biochemical analysis of pericardial fluid in hemorrhagic pericardial effusion. However, the analysis of both pericardial fluid and serum may make it possible to evaluate the cause of pericardial effusion.