Summary :We report that coval ent cross-linking of collagen mol ecul es by pyridinoline increases significantly in liver in a muri ne model of alveolar echinococcosis. The highest amount of pyridinoline per collagen mol ecul e (up to 3.5 fold the control values) is found in liver parasitic lesions. It is also increased, but to a far lesser extent, at distance from the fibrotic areas, in macroscopically normal zones of the liver, suggesting that the increase in mature collagen cross-linking occurring in the fibrogenesis due to Echinococcus multilocularis infection involves the whole liver. The comparison of these data with those we have obtai ned in another parasitic disease, muri ne schistosomiasis leading to a milder liver fibrosis, largely reversible following chemotherapy, supports a relationship between the liver pyridinoline level and the severity of liver fibrosis. Pyridinoline coul d be a tissular marker of chronic liver fibrosis in parasitic diseases.