Pericardioscopy enables endoscopic inspection and aimed biopsy of the parietal and visceral pericardium. To elucidate possible technical modifications contributing to the feasibility, diagnostic value and safety of the procedure, pericardioscopy with an Olympus HYF-1T flexible endoscope was performed in 32 patients (53.1% males, mean age 46.2 +/- 13.1 years) with pericardial effusions. In all patients, the initial step of the procedure was subxiphoid fluoroscopically controlled pericardiocentesis and drainage of the pericardial effusion. An Olympus FB-41ST biopsy forceps was applied for endoscopically guided pericardial biopsies. Standard sampling was used in 22/32 patients (3 to 6 samples/patient) and extensive sampling in 10/32 patients (18 to 20 samples/patient). In additional 12 patients pericardial biopsy was performed without pericardioscopy, under fluoroscopic control. Endoscopic visualization was clearly superior when pericardial effusion was partially replaced with 100 to 300 ml of air (29/32 procedures) in comparison to 3/32 procedures in which the pericardial effusion was replaced with warm normal saline (37 degrees C). In patients with hemorrhagic effusion (12/32), we either repeatedly injected and removed 100 to 150 ml volumes of normal saline (37 degrees C), or postponed pericardioscopy for 2 to 3 days of active drainage. The specificity of endoscopic findings is low and not decisive for the diagnosis. However, pericardioscopy is significantly contributing to the diagnostic value of pericardial biopsy, especially regarding establishing the new diagnosis and etiology of the pericardial disease. Sampling efficiency was also significantly higher for procedures using aimed pericardial biopsy with standard and extensive sampling compared to procedures performed under fluoroscopy: 86.2%, 87.3%, and 43.7%, respectively. No major complications directly related to the procedure were encountered. Minor complications included: short-run ventricular tachycardia (6.3%), pain at the sheath entry site (75%) and transient fever (37.5%). In conclusion, pericardioscopy with Olympus HYF-1T, after air instillation, is a technically complex, but safe procedure that enables excellent visualization and extensive pericardial sampling with improved diagnostic value of pericardial biopsies.