Background: Human Uncoupling Protein 3 (UCP3) is a new candidate gene for human obesity. UCPJ has been shown to be regulated by thyroid hormone, 3-adrenergic agonists, leptin, and fat feeding in rodents. Mutations in exon 3 (V1O2I) and exon 4 (R143X) were identified in obese and diabetic pro bands. Pro-opiomeleancortin (POMC), another obese gene, plays a central role in α-MSH regulation of food intake by activating melanocortin-4-receptors in the brain. The POMCgene codes for the prohormone pro-opiomelanocortin, the hormone suspected of playing a role in appetite and body weight regulation. Methods: We selected 100 obese and 300 non-obese children for analysis. Obesity was defined as a body mass index greater than or equal to the 95percentile. To examine whether mutations in exon 3 (V1O2I) and 4 (R143X) of the uncoupling protein gene might be factors for obesity in Taiwanese children, the target DNA fragments were amplified by polymerase chain reaction, and the genotypes were defined by restriction fragment length polymorphism. Results: No significant differences in the frequency of these mutations were found between obese and non-obese children. Conclusions: The results indicate that those mutations of the UCP3 and POMC genes do not playa role in the development of obesity in Taiwan's children.