10564 Background: Endothelial dysfunction, as an indicator of vascular disease in childhood cancer survivors (CCS) has not been widely studied. Methods: Markers of vascular inflammation (high sensitivity C-reactive protein [hsCRP]), hemostasis (fibrinogen), activation (endothelial cell expression of vascular cell adhesion molecule [VCAM-1]) and functional testing (large/small artery elasticity [L/SAE], pulse wave velocity [PWV]) were assessed in 200 CCS, ≥10 years from diagnosis, and 192 age/gender matched healthy controls. Exclusion criteria included: inflammatory processes, use of anti-inflammatory or cardiovascular medications, or pregnancy. Differences were assessed by adjusted multivariable linear regression. Results: CCS (53% male) of leukemia/lymphoma (59%), central nervous system tumors (6%), sarcomas (11.5%), embryonal tumors (22.5%), and other (1%) had a mean age at diagnosis 7.3 years (SD ±5.7). CCS and controls did not differ in current age (mean 34.1 ±9.2 vs. 33.5 years ±9.8), body mass index, smoking, mean systolic (124 mm Hg ±11.7 vs. 123 ±11.9) or diastolic blood pressure (73 ±9.5 vs. 71 ±9.5). Fasting low- (110 mg/dl ±31 vs. 102 ±30) and high-density (52 ±16 vs. 56 ±18) cholesterol levels differed between survivors and controls (p<0.01). Endothelial expression of VCAM-1 and PWV were statistically significantly increased in CCS; arterial elasticity was significantly reduced (table). Therapeutic exposures (anthracyclines and radiation) were not significantly associated with endothelial dysfunction. Conclusions: Childhood cancer survivors have greater endothelial dysfunction, a sign of atherosclerosis, and preventive measures should be investigated. [Table: see text]