Dry ice–baited light traps, counts of mosquitoes biting and landing on technicians, and larval surveillance were used to determine mosquito species abundance on Annette Key, Little Knockemdown Key, Little Pine Key, Raccoon Key, and the Water Keys, all of which are located offshore, within the National Key Deer Refuge and Great White Heron National Wildlife Refuge in Monroe County, FL. Due to the close proximity of these wilderness islands to the inhabited islands of the Florida Keys, it is important to understand the abundance and composition of the mosquitoes and the effects they may have on populations on inhabited islands. Thirty different species were collected during 2004–2008. Aedes taeniorhynchus, the black salt-marsh mosquito, was the most abundant mosquito species collected at all locations. Other mosquitoes collected in large numbers at all locations were Anopheles atropos, Culex bahamensis, Cx. nigripalpus, and Deinocerites cancer. Because these wilderness islands are difficult to traverse due to vegetative growth, the placement of mosquito traps close to the perimeter of the islands may influence assessment of the abundance and diversity of mosquito species collected on each island.