Chapter XX External causes of morbidity and mortality

This chapter, which in previous revisions of ICD constituted a supplementary classification, permits the classification of environmental events and circumstances as the cause of injury, poisoning and other adverse effects. Where a code from this section is applicable, it is intended that it shall be used in addition to a code from another chapter of the Classification indicating the nature of the condition. Most often, the condition will be classifiable to Chapter XIX, Injury, poisoning and certain other consequences of external causes (S00-T98). Causes of death should preferably be tabulated according to both Chapter XIX and Chapter XX, but if only one code is tabulated then the code from Chapter XX should be used in preference. Other conditions that may be stated to be due to external causes are classified in Chapters I to XVIII. For these conditions, codes from Chapter XX should be used to provide additional information for multiple-condition analysis only. Categories for sequelae of external causes of morbidity and mortality are included at Y85-Y89.