The relative suitability of two colonies established from local strains of Aedes albopictus (Wilmington and Rockingham) and a local (Raleigh) and laboratory (Liverpool) strain of Ae. aegypti to support development of Dirofilaria immitis was investigated. High levels of mortality occurred 1-2 days after mosquitoes fed on a heavily microfilaremic (28,617 microfilariae/ml) dog but not when mosquitoes were fed on a dog exhibiting a moderate microfilaremia (3,300 microfilariae/ml). At 15-16 days postfeeding, development of D. immitis to the third larval stage occurred to some extent in mosquitoes of all four strains. Microfilariae were only found in the Raleigh strain of Ae. aegypti. Aedes albopictus most frequently contained first and second stage larvae that were deteriorated which suggested that their development had been arrested. Third stage larvae were found most often in the Liverpool strain of Ae. aegypti. Colonies established from local strains of Ae. albopictus and Ae. aegypti do not appear to be suitable hosts of D. immitis.