The present study was conducted to assess the relationship between obesity and serum levels of C-reactive protein (CRP), carotenoids, oxidized LDL (oxLDL), oxidized LDL antibodies (oLAB), and leptin in Japanese residents. The subjects were 158 males and 158 females aged 40-79 years, and living in Hokkaido, Japan, who attended a health examination screening. Serum levels of CRP, oxLDL, oLAB, and leptin were measured by enzyme-linked immunosorbent assay (ELISA) and serum carotenoid levels were measured by high-performance liquid chromatography (HPLC). Body mass index (BMI) was calculated as body weight (kg) divided by height (m) squared and obesity was defined as BMI of 25 or more (kg/m2). Serum levels of CRP and leptin were significantly higher in the obese group than in their non-obese counterparts in both genders. Serum levels of beta-carotene and beta-cryptoxanthin were lower in the obese individuals, especially in females. While values for oxLDL and oLAB did not significantly vary. BMI was positively correlated with log-transformed serum levels of CRP and leptin in both genders (males: r=0.231, p<0.05; females: r=0.305, p<0.001). In females, moreover, BMI was negatively correlated with log-transformed serum levels of beta-carotene, zeaxanthin/lutein, and beta-cryptoxanthin (r=-0.244, p<0.01; r=-0.200, p<0.05; r=-0.207, p<0.01, respectively). Significantly higher odds ratios (ORs) for high serum levels of CRP (males: OR=2.12; females: OR=3.96) and leptin (males: OR=3.83; females: OR=9.07) were observed in obese versus non-obese men and women, after adjusting for various confounding factors. Significantly lower adjusted odds ratios for high serum levels of alpha- and beta-carotenes (males: OR=0.23, 0.33; females: OR=0.35, 0.39, respectively) were also observed in the obese as compared to the non-obese group. In conclusion, obesity is highly associated with states of oxidative stress and low-grade inflammation in Japanese residents, suggesting that these latter might play an important role in the association between a high BMI and certain cancers as well as coronary heart disease (CHD).