Summary 　がん患者のせん妄は頻度が高く，患者の苦痛につながるのみならずさまざまな問題を引き起こす。多くが治療に反応するため，適切な介入を行うことが重要である。せん妄の基本的治療戦略は，①医学的管理，②環境的・支持的介入，③薬物療法である。患者の個別の状況に応じて，原因の評価と対応，ゴール設定，リスクマネジメントなどの医学的管理と，見当識障害や興奮を和らげ，本人や家族の不安を軽減するための環境的・支持的介入を必ず行い，十分にせん妄症状が和らげられない場合はハロペリドールなどの抗精神病薬を中心とした薬物療法を行う。終末期では，これらに加えて死別を前にした家族へのケア，持続鎮静などのテーマも扱う必要がある。 Delirium is common among cancer patients, and is not only distressing to patients but can cause various other problems. As delirium responds to treatment in many cases, appropriate intervention is important. Treatment of delirium involves three basic strategies : 1. medical management, 2. environmental and supportive interventions, and 3. pharmacotherapy. Specific treatment will depend on the situations of individual patients, but should comprise medical management including evaluation of presumed causes and corrective measures, goal setting, and risk management, as well as environmental and supportive interventions for reduction of disorientation and agitation to alleviate anxiety in both patients and family members. If delirium is still inadequately controlled, pharmacotherapy may be started, primarily with antipsychotics such as haloperidol. If the patient is terminally ill, the care will involve other issues such as continuous sedation and pre-bereavement support for family members.