About 70% of all patients with sickle cell disease suffer from pain crises. Pain crises are recurrent episodes of pain that range in severity from mild to severe, usually occur very abruptly and are often localized around joints. Pain crises are caused by vaso-occlusions in the vascular bed of the bone marrow, leading to necrosis, edema and increased pressure. For effective analgesia morphine or morphine analogues are often required. When treating a pain crisis the patient's complaints need to be taken seriously and analgesic therapy should be started promptly with analgesics in proportion to the severity of the patient's pain. With mild pain oral non-opioid analgesics are sufficient, in moderate pain they are given in combination with oral codeine. Severe pain requires IV morphine, also combined with a non-opioid analgesic. Intravenous morphine makes a thorough monitoring of ventilation and level of consciousness mandatory. Sickle cell patients do not become drug dependent if given morphine for adequate analgesia. While bone marrow transplantation has become an accepted treatment modality for sickle cell patients with severe pain crises, treatment with hydroxyurea to increase HbF levels and reduce incidence and severity of pain crises, however, is still experimental.