Heparin induced thrombocytopenia (HIT) is a serious complication of heparin administration. In the last decade, this clinical syndrome has come into the focus of interest, primarily because of the severe thromboembolic complications that may lead to lethal outcome. In addition, great improvements have been made in the treatment with direct thrombin inhibitors and in laboratory diagnosis of HIT. As guidelines for diagnostic and management of HIT upgrade the quality of patient treatment, activities for their development have been launched in the Republic of Croatia. Based on British Committee for Standards in Haematology (BCSH) recommendations on diagnostic and treatment of HIT from 2006, activities for the introduction of new assays for anti-heparin antibodies were launched in 2008 and 2009, including algorithm of laboratory testing for HIT, sheet for clinical assessment of HIT (4T score), and education oftransfusiologists and clinicians. Upon evaluation of the results collected during one-year period, the Croatian Society of Haematology and Transfusion Medicine nominated a task force for the development of guidelines for HIT in January 2010. Following wide-ranging discussion, the guidelines were adopted in May 2011.