We have developed a procedure using a bank of temperature-sensitive (ts) mutants of fission yeast to identify mutants which can be rescued by expression of a plasmid-borne gene of interest. The procedure has been used to identify new ts alleles of cdc2 and swi7/poll, a ts mutant rescued by actin, and to identify a ts allele of cdc11 which can be rescued by combined mammalian Myc and Max expression. The procedure should also be useful as an alternative approach to identify genes in fission yeast which are functionally homologous to genes of interest from other organisms.