Chemical insecticides are the primary means to control mosquitoes, and mosquito control programs must regularly monitor for resistance of mosquito vectors to commonly used insecticides to ensure the efficacy and sustainability of active ingredients. We performed insecticide resistance bioassays to test the susceptibility of field-collected mosquitoes in central New Jersey to 1 larvicide (temephos) and 2 adulticides (malathion and sumithrin). Larval susceptibility of Culex pipiens pipiens to temephos provided median concentration (LC50) and 95% lethal concentration (LC95) values of 1.108 microg/l and 2.02 microg/l, respectively. Bottle bioassays of adult Aedes albopictus showed that 100% mortality was achieved at 35-min exposure to sumithrin and at 40-min to malathion. Baseline values were obtained using both temephos and sumithrin. Our bioassays indicate satisfactory susceptibility to temephos and sumithrin in Ae. albopictus and Cx. p. pipiens field populations in central New Jersey. Despite constant field use, both products are still effective and can be used adequately for control of the test species. However, the susceptibility of target insects to various formulations should be closely monitored periodically to ensure continual efficacy.