Motivated by the failure of current methods to control dengue fever, we formulate a mathematical model to assess the impact on the spread of a mosquito-borne viral disease of a strategy that releases adult male insects homozygous for a dominant, repressible, lethal genetic trait. A dynamic model for the female adult mosquito population, which incorporates the competition for female mating between released mosquitoes and wild mosquitoes, density-dependent competition during the larval stage, and realization of the lethal trait either before or after the larval stage, is embedded into a susceptible-exposed-infectious-susceptible human-vector epidemic model for the spread of the disease. For the special case in which the number of released mosquitoes is maintained in a fixed proportion to the number of adult female mosquitoes at each point in time, we derive mathematical formulas for the disease eradication condition and the approximate number of released mosquitoes necessary for eradication. Numerical results using data for dengue fever suggest that the proportional policy outperforms a release policy in which the released mosquito population is held constant, and that eradication in Ϸ1 year is feasible for affected human populations on the order of 10 5 to 10 6 , although the logistical considerations are daunting. We also construct a policy that achieves an exponential decay in the female mosquito population; this policy releases approximately the same number of mosquitoes as the proportional policy but achieves eradication nearly twice as fast.dengue fever ͉ genetically modified mosquitoes ͉ mathematical epidemiology W orldwide morbidity and mortality from mosquito-borne viral diseases are substantial and on the rise (1). No licensed vaccine exists for the most important of these viruses, the dengue virus, which each year causes 50-100 million cases of dengue fever and 250,000-500,000 cases of the potentially fatal dengue hemorrhagic fever (2). The Aedes aegypti mosquito (also known as Stegomyia aegypti), which is the main vector for dengue fever and yellow fever, is endemic in the southeastern U.S., and the West Nile virus spread easily through the U.S. in recent years, suggesting the U.S. could be vulnerable in coming years to both natural and deliberate outbreaks of mosquito-borne viral diseases. Given the failure of current methods to control the spread of these diseases, considerable effort has gone into novel population-suppression strategies. The sterile insect technique (SIT), which releases sterile (irradiated) male insects that mate with wild females, resulting in no progeny, has been used successfully for Ͼ50 years for control and eradication of several pests and disease vectors (3, 4). However, irradiated mosquitoes have difficulty competing with wild males for wild females (5-7) and there are no large-scale SIT mosquito programs currently in operation. A proposed alternative approach that is also environmentally benign is the release of insects carrying a dominant lethal (RIDL) strategy. In this ap...