We have cloned the SKI8 gene, one of the chromosomal genes that repress replication of M, L-A, and L-BC double-stranded RNA viruslike particles in yeast. The clone was used to map SKI8 to chromosome VII near ade5 and to construct a deletion mutant. The deletion mutant was unable to grow at 8 degrees if and only if M1 double-stranded RNA was present.