Taxol is a new anti-cancer drug that is a natural product derived from the bark of the Pacific Yew tree. The drug promotes polymerization and stabilization of tubulin to microtubules and interferes with the mitotic spindle. Clinical trials indicate that taxol is effective in the treatment of patients with refractory ovarian cancer, breast cancer, malignant melanoma and probably other solid tumors. Toxicities include anaphylactoid reactions, leukopenia, peripheral neuropathy and oropharyngeal mucositis. Increased supplies of the drug are required to support further phase II and III testing.