Tubulin was purified from yeast homogenate by DEAE-Sephadex column chromatography and temperature-dependent assembly. The yeast tubulin subunits comigrate with the brain alpha-tubulin subunit on one-dimensional sodium dodecyl sulfate gel electrophoresis. The in vitro yeast tubulin assembly is inhibited by the fungicide methyl N-(benzimidazol-2-yl)carbamate, the active component of benomyl, whereas in vitro brain 6S tubulin assembly is resistant. This suggests that the inhibitory effect of benomyl on yeast cell division is due to its antimicrotubule action.