Black flies (Diptera, Simuliidae) are small but rather robust flies, well known for the specialised feeding habits of the females. The preimaginal stages are always associated with running water and may be found in flows ranging from tiny trickles to large rivers. As filter feeders, the larvae play a key role in river and stream ecology and are important members of the food web. In many regions of the world, particular environmental factors have giben rise to mass emergences of adult black flies, and the females of many species then actively seek a bloodmeal. Bloodsucking females are important pests and are vectors of disease organisms in humans and in both domestic and wild animals. Worldwide, they are directly responsible for serious economic losses and even deaths among cattle. Within the context of medical and economic zoology, the Simuliidae are one of the best-studied groups of lotic insects. Adult black flies are able to transmit filarioid worms and blood protozoans to a wide range of vertebrates. In parts o the tropics, they are responsible for the transmission of Onchocerca volvulus, and onchocerciasis or "river blindness" is recognized as a major endemic desease, mainly in Africa and Central and South America. Based on their medical and veterinary importance, black flies require increased scientific research, for example in the areas of morphological taxonomy, systematics, freshwater ecology, molecular biology, cytogenetics, parasitology, immunology, epidemiology, and pest management. In 2004, the Simuliidae working groups of Central Europe and Great Britain met together to take part in a International Simuliidae Symposium, held from 15 to 18 September at the Humboldt-Universität zu Berlin, Germany. With 38 delegates from 16 countries (Austria, Belgium, Canada, Czech Republic, Finland, France, Germany, Great Britain, Italy, Lithuania, Norway, Serbia-Montenegro, Russia, Slovakia, Sweden, USA), this was the largest European meeting of its kind to be held. In total, 35 scientific presentations were given, with the emphasis predominantly on taxonomy and systematics, history, ecology, transmission of desease agents, medical and veterinary aspects, and control. The major part of lectures held in the symposium is presented in this current issue of the Supplementum series of Studia dipterologica. Bass, J. & Werner, D.: Studies on Simulium (Schoenbaueria) nigrum (Meigen) (Diptera: Simuliidae): a preliminary account of egg location and distribution along the banks of the River Oder (Germany). Bernotiene, R.: On the distribution of black fly larvae (Diptera, Simuliidae) in different rivers in Lithuania. Cheke, R. A. et al.: Onchocerciasis transmission by the Bioko form of Simulium yahense Vajime & Dunbar, 1975 (Diptera: Simuliidae). Ignjatovic Cupina, A. et al.: Estimating the biting risk to humans by the black fly species that are most abundant in the region of Novi Sad (Vojvodina province, Serbia and Montenegro). Jedlicka, L.: Distribution of three high altitude black fly species (Diptera: Simuliidae). Ilmonen, J. & Kuusela, K.: The black flies (Diptera, Simuliidae) recorded from Finland. Kachvoryan, E. A. et al.: Biodiversity of black flies (Diptera: Simuliidae) in relation to water quality in the Hrazdan River system of Armenia. Werner, D., Kachvoryan, E. A. & Richter, V. A.: Notes on predation by Asilidae on Simuliidae and Anthomyiidae (Diptera). Werner, D. & Pont, A. C.: The feeding and reproductive behaviour of the Limnophorini (Diptera: Muscidae). Ignjatovic Cupina, A. et al.: Notes on predation by Hydra vulgaris complex (Cnidaria, Hydrozoa) on Simulium (Boophthora) erythrocephalum De Geer, 1776 (Diptera, Simuliidae). Stloukalová, V.: Irregularities in the branching of pupal gills in Prosimulium rufipes (Meigen) (Diptera: Simuliidae). Davies, J. B.: World distribution list of the vernacular or common names given to Simuliids. Betke, P. & Werner, D.: Dr. rer. nat. habil. Günther Gräfner (1932-1997).