In 2009, an outbreak of dengue fever occurred in Yiwu, the major international market in Zhejiang province, China. A mosquito vector eradication program was undertaken using several insecticides to limit further transmission of the dengue virus. At the conclusion of this effort, the affected area was surveyed for dengue fever vector species, and mosquito-breeding area water samples were collected and analyzed for residual pesticide content. The survey detected the Asian tiger mosquito, Aedes albopictus (Skuse), in 19 villages in Yiwu, accounting for 51.7% of the mosquitoes in the 89 samples collected. Other species collected included Armigeres subalbatus (Coquillett), Culex pipiens quinquefasciatus Say, Cx. tritaeniorhynchus Giles, Cx. mimulus Edwards, and Anopheles sinensis Wiedemann. Analysis of water from 45 mosquito-breeding sites using gas chromatography-mass spectrometry detected a total of 7 pesticides, including the herbicide prometryn, 2 organophosphate insecticides (chlorpyrifos and triazophos), and 3 pyrethroid insecticides (cyhalothrin, cypermethrin, and permethrin). The maximum level of permethrin detected was 323.9 μg/L in breeding waters in which Ae. albopictus and Ar. subalbatus coexisted.