The history of the study of bloodsucking mosquitoes, sand flies, black flies, and horse flies in St. Petersburg and Leningrad Province is observed. At present, 38 mosquito species of 5 genera, 67 black fly species of 17 genera, 24 species of bloodsucking sand flies of the genus Culicoides, and 36 horse fly species of 6 genera were revealed in the territory of the region. The analysis of 267 collecting sites of 165 species of 30 genera of bloodsucking insects allowed revealing the most widespread species. The species composition of bloodsucking dipterans in the region is examined insufficiently. Till present, eastern and central (near the Ladoga Lake) parts of the region examined, and also the northern part of the Karelian Isthmus remain poorly studied. The last collections of bloodsucking insects of the "gnus" complex were performed more that 30 years ago.