OBJECTIVES: Charlson comorbidities are frequently used to describe populations and for risk adjustment in observational studies and are often identified using International Classification of Diseases, Clinical Modification (ICD-9/10-CM) codes. To date, no ICD-10-CM Charlson code list has been published for United States (US) healthcare data, although they have been published for other countries (eg, Quan et al. Med Care 2005;43:1130-9). The objective was to develop a code list for the US. METHODS: Quan’s adaption (Canadian ICD-9/10 codes) and Deyo’s adaption (US ICD-9 codes) were the starting point for developing our list. Medical coding experts conducted a medical code review with consideration of Quan and Deyo concepts. Face validity was evaluated in the Truven Health MarketScan® Databases (Commercial and Medicare Supplemental databases containing medical claims) by comparing rates of comorbidities in Q4 2014 (ICD-9) and Q4 2015 (ICD-10), using Deyo as our ‘gold standard’ for the US. RESULTS: Some additional (to Quan) relevant ICD-9 and ICD-10 codes were identified in the US, and few codes were removed (many of them due to coding differences between the US and Canada). With the exception of mild liver disease and dementia, the rate ratios comparing comorbidities using our IC D9/10 code lists versus Deyo’s in Truven Marketscan were close to 1. The rate ratios comparing our ICD-9 with our ICD-10 code list in Truven Marketscan during Q4 2014 and Q4 2015 were close to 1. CONCLUSIONS: Our ICD-9/10-CM Charlson comorbidities code list demonstrated good face validity. The higher rates of dementia and mild liver disease comorbidities in medical claims observed with our code lists appear may be the result of newer (became effective after the time of Deyo’s study) relevant codes. Charlson comorbidity codes should be revised with future ICD-10-CM changes and validated in real-world datasets.