Abstract: The super-suppressors in yeast are defined as allele specific suppressors which act upon mutants at two or more loci (HAWTHORNE and MORTIMER 1963). The properties of the suppressible alleles indicate that they are nonsense mutants (MANNEY 1964; HAWTHORNE and FRIIS 1964; FINK 1966), and thus the super-suppressors (nonsense suppressors) are analogous to the amber and ochre suppressors of Escherichia coli. To date, 22 different nonsense suppressors have been isolated. These suppressors can be assigned to 10 phenotypic classes on the basis of the spectra of mutant alleles suppressed. However, as many as 8 genetically distinct suppressors are found within a single phenotypic class. Thus the action spectrum alone is insufficient for the identification of a given suppressor. To facilitate the identification and description of the nonsense suppressors, the following studies were undertaken to locate the suppressor genes on the linkage map of yeast.