We analyzed data on renal allograft recipients over a 27-year period in order to investigate the frequency, etiology, and outcome of pericarditis developing during the first two months following renal transplantation. Of the 1497 patients receiving renal transplants between 1963 and 1990, 34 patients developed 36 episodes of pericarditis and/or pericardial effusions, for an overall incidence of 2.4%. Pericarditis was attributed to uremia in 14 episodes, cytomegalovirus infection in three, both uremia and CMV infection in four, nonspecific bacterial infection in three, and tuberculosis and minoxidil therapy in one episode each. No etiologic diagnosis could be established in 10 episodes. No statistically significant differences were found between pericarditis and case-matched control patients considering demographic features, the number of immediately functioning grafts, the duration of posttransplant acute renal failure, the number of supportive dialysis days, pre- and postoperative CMV status of the patients, and pretransplant BUN and serum creatinine levels. There were more uremic-related complications (pulmonary edema, gastrointestinal bleeding, central nervous system symptoms) in the pericarditis group. Five allografts in the pericarditis group never functioned, versus only one in the control group. Three patients with pericarditis developed pericardial tamponade. Early diagnosis, close follow-up, and in the case of cardiac tamponade early invasive treatment, should improve the prognosis of this potentially life-threatening complication.