Abstract
Two high mol. wt. double stranded RNA species have been discovered in yeast; some strains possess both species (killers) whilst other strains possess only one. Strains of the latter type have been isolated which possess relatively large amounts of dsRNA. Cell fractionation experiments utilizing these strains have shown that the dsRNA is associated with isometric virus-like particles similar to those found in other fungi. Similar particles, containing both species of dsRNA, have been isolated from a killer strain. The two species of dsRNA appear to be separately encapsidated.