Context: Adult survivors of childhood cancer are at risk for medical and psychosocial sequelae that may adversely affect their health status. Objectives: To compare the health status of adult survivors of childhood cancer and siblings and to identify factors associated with adverse outcomes. Design, Setting, and Participants: Health status was assessed in 9535 adult participants of the Childhood Cancer Survivor Study, a cohort of long-term survivors of childhood cancer who were diagnosed between 1970 and 1986. A randomly selected cohort of the survivors' siblings (n=2916) served as a comparison group. Main Outcome Measures: Six health status domains were assessed: general health, mental health, functional status, activity limitations, cancer-related pain, and cancer-related anxiety/fears. The first 4 domains were assessed in the control group. Results: Survivors were significantly more likely to report adverse general health (odds ratio [OR], 2.5; 95% confidence interval [CI], 2.1-3.0; P<.001), mental health (OR, 1.8; 95% CI, 1.6-2.1; P<.001), activity limitations (OR, 2.7; 95% CI, 2.3-3.3; P<.001), and functional impairment (OR, 5.2; 95% CI, 4.1-6.6; P<.001), compared with sibiings. Forty-four percent of survivors reported at least 1 adversely affected health status domain. Sociodemographic factors associated with reporting at least 1 adverse health status domain included being female (OR, 1.4; 95% CI, 1.3-1.6; P<.001), lower level of educational attainment (OR, 2.0; 95% CI, 1.8-2.2; P<.001), and annual income less than $20000 (OR, 1.8; 95% CI, 1.6-2.1; P<.001). Relative to those survivors with childhood leukemia, an increased risk was observed for at least 1 adverse health status domain among those with bone tumors (OR, 2.1; 95% CI, 1.8-2.5; P<.001), central nervous system tumors (OR, 1.7; 95% CI, 1.5-2.0; P<.001), and sarcomas (OR, 1.2; 95% CI, 1.1-1.5; P=.01). Conclusion: Clinicians caring for adult survivors of childhood cancer should be aware of the substantial risk for adverse health status, especially among females, those with low educational attainment, and those with low household incomes.