Abstract Background: Leukemia is the most common malignancy in children. The etiology of childhood leukemia is mostly unknown, although some environmental factors such as ionizing radiation and parental alcohol and tobacco use may play a causative role in leukemia. Methods: To investigate the association between parental alcohol consumption and childhood leukemia in a hospital-based case-control study in Korea, histologically-confirmed incident childhood leukemia cases (n=365) aged 0-18 years old were recruited from three teaching hospitals located in Seoul, Korea, between May 2003 and August 2008. Non-cancer controls (n=558) aged 0-18 years old without medical history of childhood cancer were recruited from the Department of Pediatrics of the same hospitals. Controls were frequency-matched to cases by 5-year age intervals and sex (cases: controls=1:1). Leukemia risks were estimated as odds ratios (ORs) and 95% confidence intervals (CIs) using unconditional logistic regression analysis adjusted for age, sex, parent's education, and birth weight (<3.25, 3.25-3.70, ≥3.70 kg). In addition to conducting analyses of all childhood leukemia, we calculated histologic subtype-specific ORs for acute lymphoblastic leukemia (ALL; n=200) and acute myeloid leukemia (AML; n=88). Results: Among general characteristics, higher birth weight and parental education were associated with childhood leukemia risk (P<0.05). The proportion of drinking mothers was significantly higher among all leukemia cases than controls (58% vs. 49%: OR=1.4, 95% CI=1.00-1.83), whereas no association was observed for paternal alcohol consumption (87% vs. 83%). When the analysis was restricted to AML cases, the association between maternal drinking and cancer risk became stronger (OR=1.8, 95% CI=1.06-2.90). Drinking frequency of the mothers was also associated with the increased risk. (≥1/month vs. <1/month; OR=1.7, 95% CI=1.10-2.28). Also, drinking duration of more than one year before pregnancy increased the risk of AML (OR=1.7, 95% CI= 1.00-2.85). No association was found between parental alcohol consumption and ALL risk. Conclusion: Our results suggest that maternal alcohol consumption is associated with AML among Korean children. However, larger studies need to be conducted to replicate our findings. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1825.