The history of development of paclitaxel (TAXOL [Bristol-Myers Squibb Co., Princeton, NJ]) is a long story and serves as a model of perseverance for those involved in drug development. Notations of the use of products of the yew tree date back to the Celts, but it was in the 1950s to the 1960s that the National Cancer Institute (NCI) selected the product for trials and the current process began. The active agent was identified in the 1970s, and when its unique mechanism of action was isolated in 1979, interest reemerged. Paclitaxel is an antimicrotubule agent that, unlike other antimicrotubule agents, promotes microtubule assembly. This unique mechanism of action has generated considerable interest in oncology. The clinical trials in the 1980s documented the drug's safety, identified its side effects, and demonstrated its activity in patients with ovarian cancer who had received prior treatment. The many clinical trials currently under way will provide information on the drug's range of activity. Paclitaxel's development has been an arduous process. Its development and supply initially were complicated, but these hurdles have been overcome, and the drug's unique mechanism of action and initial clinical trial results hold promise in the 1990s.