The acute-phase response consists in a large number of behavioural, physiologic, biochemical, and nutritional changes involving many organ systems distant from the site, or sites, of inflammation. One of the most investigated, but still not well understood, characteristic of the acute phase is the up-regulation, or down- regulation, of many plasma proteins, known as the acute-phase proteins. The changes in the concentrations of these positive acute-phase proteins and negative acute-phase proteins are due to changes in their liver production. Their increase may vary from 25 percent to 1000 fold, as in the case of C-reactive protein and serum amyloid A. This review summarises the recent advances that have been acquired on the acute-phase proteins, in particular their function in pathologies such as infections or inflammatory lesions.