Thirty-six wild type isolates of Neurospora were surveyed for the presence of dsRNA. The survey identified seven strains which contain dsRNA molecules. These seven strains are all from different geographic locations. The sizes of the dsRNAs range from 500 bp to 18 kb and a total of seven distinct dsRNA species was identified. Cross homologies of some of the dsRNAs were apparent. There was homology between the 9.0 kb dsRNA and genomic DNA prepared from all strains in the survey, indicating a possible cellular rather than viral origin for this dsRNA species. None of the other dsRNAs hybridized with genomic DNA suggesting a viral origin for these dsRNAs.