Two species of mosquitoes reared to adults from field-collected larvae or egg rafts in or near Los Angeles County, CA, were exposed to dogs with known levels of Dirofilaria immitis (Leidy) microfilariae per 20 cubic millimeters of blood. Aedes taeniorhynchus (Wiedemann) readily blood fed on an infected dog ingested microfilariae but did not become infected. Culiseta incidens (Thomson) also fed on an infected dog became infected, and 10% of the microfilariae developed to the L3 stage. Cs. incidens is a peridomestic species broadly distributed in Los Angeles County and abundant from February through December. The wide distribution of this species as well as its long annual period of reproductive activity in Los Angeles County may contribute to its potential as a vector of D. immitis.