Crimean Congo Hemorrhagic Fever (CCHF), which has been described in about 30 countries until today, is a fatal disease. Humans usually get infected by bites of ticks, contact with a patient in the acute phase of the disease or contact with the blood or tissues of viremic livestock. The occurrence of CCHF closely approximates the known world distribution of ticks of the Hyalomma species. The novel studies of phylogenetic analyses reveal interesting data about relations between distant strains. The clinical features exhibit a dramatic progress characterized by hemorrhage, myalgia and fever. The levels of liver enzymes, creatinine phosphokinase and lactate dehydrogenase are elevated; bleeding tests are prolonged. In the pathogenesis, infection of the endothelium plays a major role. Besides the direct infection of the endothelium, endothelial activation and damage can also occur by host factors formed due to the effect of the virus. In diagnosis, enzyme-linked immuno-sorbant assay (ELISA) and real-time reverse transcription polymerase chain reaction (RTPCR) are used. Early diagnosis and supportive treatment are important. Ribavirin was found to be beneficial in some studies. In endemic areas, people exposed to tick bites and health care workers are under risk, especially those caring for patients with bleeding from the mouth, gums, nose, vagina or injection sites. Simple barrier precautions are usually adequate for protection.