Intensive care is increasingly used in the management of cancer patients. The main reasons for admitting a cancer patient to an intensive-care unit are postoperative recovery, critical complications of the cancer disease and its treatment, the administration and monitoring of intensive anticancer treatment, and acute disease unrelated to cancer or its treatment. The present review is focused on the prognosis of critically ill cancer patients, on the description of the types of complications requiring intensive care, on specific aspects of the application of critical-care techniques in cancer patients, on ethical considerations and on ICU organization in the context of oncology.