Mutants resistant to the antimitotic compounds thiabendazole and methyl-2-benzimidazole-carbamate were isolated and analyzed genetically in the fission yeast. Schizosaccharomyces pombe. They comprised three groups in terms of genetic linkage. Mutants in one linkage group (ben1) differed phenotypically from those in the other two (ben2 and ben3). The former were resistant to the compounds at any physiological temperature tested, whereas the latter exhibited temperature dependent resistance. Through tetrad analysis, ben1 was mapped at the rightmost part of chromosome II, and ben2 was mapped near the centromere of the same chromosome. Haploidization experiments revealed the location of ben3 on chromosome II. By analogy with Aspergillus nidulans, it is suggested that one of these ben genes may code for tubulin.