Eur J Clin Invest 2009 Surgical treatment of abdominal wall hernia has been based for many decades on observational evidence, as the disease physiopathology was ambiguous. The long-standing hypothesis of abnormal collagen metabolism as a causative factor of hernia disease seems to become substantiated by modern investigations, demonstrating a link between abnormal matrix metalloproteinase (MMP) expression and abdominal wall hernia. Current evidence suggests a strong correlation between MMP-2 and direct inguinal hernia, while the role of this MMP in indirect, incisional and recurrent hernias has not been completely elucidated yet. Furthermore, MMP-1 and MMP-13 seem to be implicated in the physiopathology of recurrent hernia, while limited data link MMP-1 also with incisional hernia formatio...