Chemical compounds that interfere with microtubules such as the vinca alkaloids and taxanes are important chemotherapeutic agents for the treatment of cancer. As our knowledge of microtubule-targeting drugs increases, we realize that the mechanism underlying the anti-cancer activity of these agents may mainly lie in their inhibitory effects on spindle microtubule dynamics, rather than in their effects on microtubule polymer mass. There is increasing evidence showing that even minor alteration of microtubule dynamics can engage the spindle checkpoint, arresting cell cycle progression at mitosis and eventually leading to apoptotic cell death. The effectiveness of microtubule-targeting drugs for cancer therapy has been impaired by various side effects, notably neurological and hematological toxicities. Drug resistance is another notorious factor that thwarts the effectiveness of these agents, as with many other cancer chemotherapeutics. Several new microtubule-targeting agents have shown potent activity against the proliferation of various cancer cells, including cells that display resistance to the existing microtubule-targeting drugs. Continued investigation of the mechanisms of action of microtubule-targeting drugs, development and discovery of new drugs, and exploring new treatment strategies that reduce side effects and circumvent drug resistance may provide more effective therapeutic options for cancer patients.