Background: Obesity has become the most common and costly metabolic problem in the world, and the genetic and environmental effects on the generation of obesity have become one of the focus factors in obesity research. Gene-chips have been reported as a useful tool in human adipose tissue research. Objective: To determine the peripheral blood gene expression profile of Chinese adult obesities by gene chip technique for the first time. Design: Randomized controlled observation. Setting: Beijing University of Traditional Chinese Medicine. Participants: The experiment was performed at the Basic Medical College of Beijing University of Traditional Chinese Medicine between August 2003 and May 2004. Five obese patients, 4 males and 1 female, aged (21.4 ± 0.9) years and three non-obese persons, 2 males and 1 female, aged (26.0 ± 5.3) years were selected by the international body mass index (BMI) standard. The written informed consent was obtained from all subjects, and the research was approved by the medical ethical committee of Beijing University of Traditional Chinese Medicine. Methods: Total RNA was extracted from peripheral blood, amplified and labeled. The quality and quantity of the processed samples were checked by Test3 array. The gene expression profiles were monitored by U133A set. The data was analyzed statistically, and the gene-symbols with significant difference were searched in Gene BANK database. Main Outcome Measures: Gene expression signal. Results: Compared with non-obese adults, 66 genes showed up-regulated expression and 28 genes showed down-regulated, of which 11 genes were up-regulated above twofold, and 6 genes were down-regulated above twofold. The results demonstrated that HLA-DQA1 (human leucocytic antigens), CRAT, MAPK813 and DKFZP434N1923 genes were up-regulated above 4 fold, and HLA-DQA1 gene was even up-regulated above 20 fold. Conclusion: Significant differences in peripheral blood gene expression profiles in Chinese adult obesities are found for the first time. The results indicate that obesity is strongly associated with MHC class II antigen HLA-DQA1, and HLA-DQB1, etc.