<ul><li><strong>BACKGROUND</strong>: To determine the prevalence of metabolic syndrome in survivors of childhood leukemia in Isfahan, Iran.</li><li><strong>METHODS</strong>: During a 4-year period (2003 to 2007), 55 children (33 male and 22 female) diagnosed with ALL at Unit of Hematology/ Oncology, Department of Pediatrics, Isfahan University of Medical Science, were enrolled in this crosssectional study. Metabolic syndrome was defined using the modified version of Adult Treatment Panel (ATP III) criteria. Insulin resistance was defined based on the homeostasis model assessment index (HOMA-IR).</li><li><strong>RESULTS</strong>: The mean age of participates was 10.4 years (range 6-19 years) and the mean interval since completion of chemotherapy was 35 months. Twenty percent (11/55) of survivors (10 male, 1 female) met criteria for diagnosis of metabolic syndrome. Obesity was observed in one forth of patients and nearly 3/4 of obese patients had metabolic syndrome. High serum insulin levels were found in 16% of participants and in 63% of obese survivors. The mean insulin levels in survivors with metabolic syndrome was three-times more than those without (28.3 mu/l vs. 9.57 mu/l, p = 0.004). Insulin resistance was detected in 72.7% of survivors with metabolic syndrome and it was&nbsp; ositively correlated with serum triglycerides (0.543, p < 0.001), systolic and diastolic BP (0.348, p = 0.01 and 0.368, p = 006 respectively), insulin levels (0.914, p < 0.001) and blood sugar (0.398, p = 003).</li><li><strong>CONCLUSIONS</strong>: The prevalence of metabolic syndrome in survivors of childhood leukemia in Iran is higher than developed countries. Nearly all of the obese patients had metabolic syndrome. Weight control and regular physical exercise are recommended to the survivors.</li><li><strong>KEYWORDS</strong>: Acute lymphoblastic leukemia, metabolic syndrome, obesity, children.</li></ul>