A total of 5,038 species of the order Diptera (Nematocera – 1,672 species, Brachycera – 3,366 species), belonging to 110 families, have been established in Bulgaria so far. The families Chironomidae (327 species – 6.5%) of Nematocera and Tachinidae (425 species – 8.4%) of Brachycera are the most numerous. The distribution of dipterans in the different regions of Bulgaria is presented. The vertical distribution of the families is considered. The greatest number of species has been found in the zone of the xerothermic oak forests (3,362 species – 66.7%). The dipterous fauna can be divided into two main groups: 1) species with a Mediterranean type of distribution (515 species – 10.2%) – more thermophilic and distributed mainly in the southern parts of the Palaearctic and the lower parts of the mountains; 2) species with a Palaearctic and Eurosiberian type of distribution (4,377 species – 87.2%) – more eurybiontic and widely distributed in the Palaearctic. The endemic species are 128 (2.5%). The distribution of the zoogeographical categories in the separate vegetation belts of Bulgaria is scrutinized. Of the established species, 61 are forestry or agricultural pests and 75 species are of human or veterinary medical significance. The bibliography contains 1374 publications.