We present the case of a 55-year-old man who developed massive pericardial effusion with tamponade within a 5-day period. During transthoracic two-dimensional echocardiographic examination, spontaneous echo contrast was visualized in pericardial effusion. A diagnosis of polymicrobial pyopericarditis was made when urgent pericardiocentesis revealed a significantly foul odor and purulent fluid that grew a culture of aerobes. After surgical drainage and appropriate antimicrobial therapy, this patient's pyopericarditis resolved. It was suggested that spontaneous echo contrast in pericardial effusion could be induced by non-gas-forming pyogenic cells.