Patients with many recurrences of acute pericarditis are commonly alarmed by the fear of constriction. We studied their long-term outcome and the possible presence of systemic diseases. Sixty-one Italian patients (36 men) were followed for an average of 8.3 years according to a predefined protocol, including testing for autoimmune diseases and familial Mediterranean fever. Symptomatic pericarditis lasted from 1 to 43 years (mean 5.4 years). Fifty-two patients had been referred to us after failure of previous therapies, including steroids. We observed 378 attacks with a mean of 1.6 per patient per year and 156 hospital admissions. Thirteen patients had a post-cardiac injury syndrome. In 43 (70.5%), the pericarditis remained idiopathic, whereas we made a new diagnosis of rheumatoid arthritis in 1 and of Sjogren's syndrome in 4 patients, but in these patients pericarditis represented the dominant clinical manifestation. Cardiac tamponade occurred during the initial attacks in 4 patients (6.5%) but never recurred. Pleural effusions were present during the first attack in 22 patients (36.0%) and liver involvement in 5 (8%). No patients developed constrictive pericarditis. Echocardiographic examination produced no evidence of chronic myocardial disease. Response to therapy was good. Thirty-one patients (50.8%) are in sustained remission, without any therapy; their total observation period has averaged 10.3 years. In idiopathic patients, antinuclear antibodies were present in 56.2% and anti-Ro/SSA in 8.3%. Mutations linked to familial Mediterranean fever were absent. In conclusion, in this large series of difficult patients with recurrent acute pericarditis and a very long follow-up, the long-term prognosis is good.