Pericardial effusions causing pericardial tamponade are rare in patients with systemic lupus erythematosus (SLE). The goal of this study is to describe in detail the clinical and laboratory characteristics of a group of patients with pericardial effusions and pericardial tamponade secondary to SLE. We retrospectively reviewed the records of 71 patients with SLE, admitted to our Hospital between 1985 and 2006 with a diagnosis of pericarditis, pericardial effusion and tamponade. Clinical features in the patients with tamponade were compared with those with pericardial effusions without tamponade. Pericardial effusion and SLE was confirmed in 41 patients. Pericardial tamponade occurred in nine of these patients (21.9%) at the time of presentation. All tamponade patients were women. Patients with pericardial effusions who developed tamponade had a statistically significant (P = 0.05) lower C4 level as compared with patients who did not develop tamponade. A pericardial window was required in five patients even though the patients were receiving high-dose corticosteroids. In the present series, all patients with tamponade were treated with high-dose corticosteroids though five of nine patients required a pericardial window in contrast to previous studies. A low C4 level at presentation was predictive of the development of tamponade physiology.