Two genes, nda2 and nda3, previously defined by cold sensitive nuclear division arrest (nda) mutations in the fission yeast Schizosaccharomyces pombe were studied. A mutant nda2-KM52 was found to be supersensitive (at the permissive temperature) to the tubulin-binding drugs such as thiabendazole, methylbenzimidazol-2yl carbamate and nocodazole. A single mutation in nda2 appears to cause both drug supersensitivity and cold sensitivity. The defective phenotypes of nda2-KM52 with a low concentration of the drugs were characterized by nuclear displacement and anomalously situated spindle pole bodies. The allele of the other mutant, nda3-KM311, was sh216 to be linked closely to the ben1 locus, which determines resistance to the drug. The identity of ben1 and nda3 genes was proved by a newly isolated mutant ben1-TB1005; it manifests ben1 resistance and the cold sensitive nda3 phenotype. At 22 degrees C, ben1-TB1005 showed cell branching and deformation characteristic of nda3-KM311. Eleven mutants supersensitive to thiabendazole were newly isolated by replica plating. Four strains were mapped in nda2, while the other four were in nda3. Most of the isolated mutants were blocked at nuclear division in the presence of a low concentration of the drug. Thus, the products of genes nda2 and nda3 (ben1) interact directly or indirectly with the drugs and control, in different ways, microtubular organization in the cells of S. pombe.