We have purified microtubule-associated proteins from Neurospora crassa on the basis of heat stability and affinity to calmodulin. Two proteins of molecular masses 170 kDa and 190 kDa have been partially purified. A third protein of 145 kDa was purified almost to homogeneity, and we present evidence that this protein is a specific substrate for a Ca²⁺/calmodulin-dependent protein kinase. The purified 170-, 190-, and 145-kDa proteins induce the assembly of microtubules from purified porcine brain tubulin. We demonstrate that all three proteins are microtubule-associated proteins on the basis of an in vitro microtubule-binding assay.