The aquatic hyphomycetes are a group of world-wide distributed fungi (Moniliales, Fungi Imperfecti) which are present in running waters. The group was recognized by Ingold (1942) from a stream in Leicestershire, England on submerged leaves of Alnus glutinosa (L.) Gaerth. He reported sixteen species. Since then this group of fungi has been found to be present in leaves, branches and twigs of different dicotyledonous plants;The Iowa aquatic hyphomycete flora has been known from only one survey conducted by Dyko in 1971-1972 at four aquatic sites in central Iowa (Dyko, 1973). The present study is a survey of aquatic hyphomycetes in two different kinds of aquatic sites in Iowa, including the northeast part of the state which has not been surveyed. The muddy streams and rivers in central Iowa could be quite different habitats from those flowing over limestone in the northeast part of the state;Eighteen species were collected during this study. Seven of these, Anguillospora gigantea Ranzoni, Articulospora tetracladia Ingold, Clavariopsis aquatica De Wildeman, Heliscus lugdunensis Saccardo & Therry, Lemonniera pseudofloscula Dyko, Lunulospora curvula Ingold, Sigmoidea prolifica Crane and Varicosporium elodeae Kegel, have not been previously reported as occurring in Iowa. Ten other species were previously reported in the state. Four species, Anguillospora gigantea Ranzoni, Articulospora tetracladia Ingold, Sigmoidea prolifica Crane and Varicosporium elodeae Kegel, were collected only in the northeast portion of the state;The observation of Clavariopsis aquatica De Wildeman, Heliscus lugdunensis Saccardo & Therry, Lemonniera pseudofloscula Dyko, Lunulospora curvula Ingold, and the absence of Centrospora curvula and Lemonniera aquatica, are the major differences in species composition of the aquatic hyphomycete flora of central Iowa as determined in Dyko's 1971-1972 investigation and the present study;References;Dyko, B. J. 1973. Aquatic hyphomycetes from four sites on theSkunk River and one site on Squaw Creek, Story County, Iowa.M. S. Thesis Iowa State University, Ames, Ia. 93 pp;Ingold, C. T. 1942. Aquatic hyphomycetes of decaying alder leaves. Trans. Brit. Mycol. Soc. 25:339-417.