ABSTRACT:The acute phase response is a complex systemic early-defence system of reactions activated by trauma, infection, tissue damage, inflammation, stress or neoplasia. One of the most important elements of this response is the increased hepatic synthesis of some plasma proteins, collectively known as acute phase proteins. The discovery of these new biomarkers has allowed the clinical monitoring of different diseases; therefore, their clinical application has been studied widely in human medicine in order to improve the diagnosis, evaluation, treatment, prognosis and therapeutics of many diseases. Although a wide range of studies have been carried out to determine the usefulness of acute phase proteins in several diseases also in animals, they are still relatively under-utilised in veterinary medicine, predominantly in farm animals. The acute phase response and clinical application of acute phase proteins in ruminants are reviewed in this article, including their diagnostic use in clinical practice and application in the monitoring of treatment, which is one of the most promising practical uses of these proteins.