BACKGROUND The clinical significance of pericardial biopsy is controversial. The aim of this study was to assess the feasibility and diagnostic value of 3 approaches to pericardial biopsy: fluoroscopic control and standard sampling, pericardioscopy guidance with standard sampling, and pericardioscopy guidance with extensive sampling. RESULTS Forty-nine subsequent patients with a large pericardial effusion underwent parietal pericardial biopsy. In group 1 (12 patients, 66.7% males, age 46.7+/-12.2 years), pericardial biopsy was guided by fluoroscopy (3 to 6 samples per patient). Group 2 included 22 patients (50% males, age 50.8+/-10.4 years) undergoing 4 to 6 pericardial biopsies per patient guided by pericardioscopy (16F flexible endoscope). In group 3, extensive pericardial sampling was performed, guided by pericardioscopy (15 patients, 53.3% males, age 53.7+/-12.8 years, 18 to 20 samples per patient). Sampling efficiency was better with pericardioscopy (group 2, 84.9%; group 3, 84.2%) compared with fluoroscopic guidance (group 1, 43.7%; P<0.01). Diagnostic value was defined as a new diagnosis uncovered, etiology revealed, clinical diagnosis confirmed, and the biopsy false-negative. Pericardial biopsy in group 3 had higher diagnostic value than in group 1 in revealing new diagnosis (40% versus 8.3%, P<0.05) and etiology (53.3% versus 8.3%, P<0.05). In group 2, pericardial biopsy had a higher yield in establishing etiology than in group 1 (40.9% versus 8.3%; P<0.05). Pericardial biopsy was false-negative in 58.3% in group 1 in contrast to 6.7% in group 3 (P<0.01). There were no major complications. CONCLUSIONS Pericardioscopic guidance enhanced pericardial sampling efficiency. The diagnostic value of pericardial biopsy was significantly improved by extensive sampling made possible by pericardioscopy.