1) Thirty-eight cases of idiopathic pericarditis in our institutes were analyzed and were classified into 3; group A: clinical picture of pericarditis, group B: clinical picture of peri-myocarditis and group C: dominant clinical picture of chronic pericardial effusion. 2) All cases of group A showed a good clinical course. 3) In group B cases with complete A--V block continued to have heart block with significant myocardial changes, and the prognosis may not be good. 4) Many cases of group C belonged to elderly female and the etiology was unclear. 5) Viral pericarditis was proven in only one case.