Purpose: To investigate the physical and biochemical parameters related with elevated serum alanine aminotransferase (ALT) levels in obese children. Methods: One hundred forty-two obese or overweight children who visited the out-patient clinics of Chungnam National University Hospital between January 2006 and August 2008 were enrolled. Physical measures and biochemical tests were performed in all patients. Liver sonography was performed in 43 patients. They were divided into the following 2 groups based on ALT levels: group I, normal ALT levels (n=65); and group II, elevated ALT levels (n=77). We compared the physical measures, biochemical results, and ultrasonographic findings of the livers in both groups. Other causes of elevated serum ALT levels were ruled out. Results: The male-to-female ratios were 1.6:1 in group I and 7.6:1 in group II. Among physical parameters, the waist circumference-to-height ratio and hip circumference-to-height ratio were significantly higher in group II (p=0.001 and 0.046, respectively). Among biochemical parameters, aspartate aminotransferase (AST), ${gamma}$-glutamyltransferase (${gamma}$-GT), and total cholesterol levels were significantly higher in group II (p<0.001, 0.001, and 0.001, respectively). The AST/ALT ratio was <1 (mean, 0.55) and statistically lower in group II. There was a positive correlation between the serum ALT level and ${gamma}$-GT (p<0.001, r=0.750), and a positive correlation between the serum ALT level and the waist circumference-to-height ratio in group II (p<0.001, r=0.401). Conclusion: The results suggest that the waist circumference-to-height ratio and ${gamma}$-GT may be associated with elevated alanine aminotransferase activity in obese children.