Surgical bile flow restoration in extrahepatic biliary atresia (EHBA) does not prevent the development of ongoing hepatic fibrosis and cirrhosis. Portal connective matrix was studied on liver biopsies obtained from seven children submitted to portoenterostomy. Electron microscopy and immunohistochemical techniques (using specific antibodies directed against collagen isotypes and associated glycoproteins) were performed. The study of extracellular and cellular components of connective mat ix demonstrated the existence of two distinct areas according to their situation with regard to ductular proliferation: loose connective matrix - mainly composed of fi, iectin, type 111 collagen, type 1V collagen and laminin - associated with microvessels and myofibroblasts proliferation characterized periportal zones adjacent to bile ductules; in areas distant from ductular proliferation, connective matrix appeared dense, composed of type I and type 111 collagen associated with fibroblasts. The connective matrix pattern observed in periductular areas can be compared to that described in cicatricial and hypertrophic processes where the myofibroblastic cell population is known to play an important role in fibrosis development. Although the connective matrix activation process remains unclear in EHBA, it may be suggested that activation of a connective tissue cellular clone might be responsible for this portal fibromatosis