Background/Aims: Prothrombin induced by vitamin K defi-ciency or antagonist II (PIVKA-II) is a widely used diagnostic marker for hepatocellular carcinoma (HCC). We evaluated the correlation between alcoholic liver disease (ALD) and serum PIVKA-II levels in chronic liver disease (CLD) patients. Methods: We retrospectively reviewed the medical records of 2,528 CLD patients without HCC. Among these patients, 76 exhibited serum high PIVKA-II levels of >125 mAU/mL (group 1). We categorized 76 control patients matched by age, sex, and the presence of liver cirrhosis from the remain-ing patients who were negative for serum PIVKA-II (group 2). Results: Group 1 revealed increased antibiotic usage (23.7% vs 2.6%, p<0.001) and incidence of ALD (60.5% vs 14.5%, p<0.001) as well as elevated aspartate aminotransferase (52.5 IU/L vs 30.5 IU/L, p=0.025) and γ glutamyl transpepti-dase (67.5 IU/L vs 36.5 IU/L, p=0.005) levels compared with group 2. Further, group 1 was significantly associated with a worse Child-Pugh class than group 2. In the multivariate anal-ysis, ALD (odds ratio [OR], 7.151; p<0.001) and antibiotic us-age (OR, 5.846; p<0.001) were significantly associated with positive PIVKA-II levels. Conclusions: Our study suggests that ALD and antibiotics usage may be confounding factors when interpreting high serum PIVKA-II levels in patients without HCC. Therefore, serum PIVKA-II levels in patients with ALD or in patients administered antibiotics should be interpreted with caution. (Gut Liver, 2015;9:224-230)