Patients with essential thrombocythemia carry a high risk for thromboembolic and bleeding events but they have an almost normal life expectancy. A careful evaluation of the medical history and an exact diagnosis is mandatory to estimate each patient's risk for morbidity and to choose the most appropriate treatment measure. In patients with the need of cytoreductive therapy, the benefits of therapy have to outweigh the potential risks of drug toxicities. Hydroxyurea is the most useful cytoreductive drug for elderly patients; in younger persons, interferon alpha or anagrelide may be the drugs of choice. The combination of anagrelide with acetylsalicylic acid may be contraindicated in patients with a history of bleeding.