Pericarditis is an inflammation of the membrane covering the exterior of the heart. Pericarditis can be acute or chronic and according to the nature of the exudate, may be fibrinous, serofibrinous, purulent, hemorragic, chilous or neoplastic. The disease appears at 0,2-0,3% of children who are hospitalized. The autors present the pediatric peculiarities through the following three cases. The first two cases were infectious: a fibrinous pericarditis caused by a virus (coxsackie B), and a bacterial pericarditis determinated by E.coli. In the third case there is a chylopericardium associated with lymphedema congenitale.