Background: Research on spending persistence has not focused on Medicaid and the Children's Health Insurance Program (Medicaid/ CHIP), which includes a complex and growing population. Objective of the Study: The objective of the study was to describe patterns of expenditure persistence, mortality, and disenrollment among nondually eligible Medicaid/CHIP enrollees and identify factors predicting these outcomes. Research Design: The study is based on New Jersey Medicaid/ CHIP claims data from 2011 to 2014. Descriptive and multinomial regression methods were used to characterize persistently extreme spenders, defined as those appearing in the top 1% of statewide spending every year, according to demographics, Medicaid/CHIP eligibility, nursing facility residence, patient risk scores, and clinical diagnostic categories measured in 2011. Similar analyses were done for persistently high spenders ( ie, always in the top 10% but not always top 1%) as well as decedents, disenrollees, and moderate spenders ( ie, at least 1 year outside of the top 10%). Subjects: Nondually eligible NJ Medicaid/CHIP enrollees in 2011. Results: One fourth of extreme spenders in 2011 remained in that category throughout 2011-2014. Almost all ( 89.3%) of the persistently extreme spenders were aged, blind, or disabled. Within the aged, blind, or disabled population, the strongest predictors of persistently extreme spending were diagnoses involving developmental disability, HIV/AIDS, central nervous system conditions, psychiatric disorders, type 1 diabetes, and renal conditions. Individuals in nursing facilities and those with very high risk scores were more likely to die or have persistently high spending than to have persistently extreme spending. Conclusions: The study highlights unique features of spending persistence within Medicaid/CHIP and provides methodological contributions to the broader persistence literature.