In utero exposure to organochlorine pesticides (OCPs) is thought to be potentially harmful to fetal development. We aimed to investigate the associations of maternal and cord serum OCPs levels with infant birth weight in China. In this study, we measured serum levels of 18 OCPs in 81 mother-infant pairs, including DDT, hexachlorocyclohexanes (BHC), hexachlorobenzene (HCB), heptachlors, chlordanes, endosulfan-I, and mirex using a high-resolution-gas-chromatography with high-resolution-mass-spectrometry method. We found that p,p'-DDE and β-BHC had the highest detection rate in both maternal and cord blood serum (97.2% and 96.7%, respectively), followed by HCB (93.0%, 51.7%), p,p'-DDT (88.7%, 36.7%), and p,p'-DDD (83.1%, 60.0%). Among all OCPs, the concentration of p,p'-DDE was the highest (mothers geometric mean (GM): 203.54ngg(-1), newborns GM: 116.14ngg(-1)), followed by HCB (70.62ngg(-1), 65.16ngg(-1)), and β-BHC (67.67ngg(-1), 33.39ngg(-1)). Multiple linear regression analyses showed that each 1ngg(-1) increment of cord serum p,p'-DDE, total DDT, and β-BHC was associated with a 0.10g, 0.10g, and 0.92g decrease in infant birth weight, respectively, and as the cord serum concentrations of p,p'-DDT, p,p'-DDD, HCB and mirex increased, the infant birth weight was also decreased, although the associations were not statistically significant due to the relatively small sample size. These results suggest that p,p'-DDE, β-BHC, and HCB were the predominant OCPs in the serum of Chinese pregnant women and cord blood of their newborns. Prenatal exposure to DDT, β-BHC, HCB, and mirex were associated with a decrease in birth weight, but these results need validation in larger sample-sized studies. Copyright © 2014 Elsevier Ltd. All rights reserved.