Paclitaxel is one of the most active new agents introduced in cancer therapy in the last decade. Results from both completed and ongoing Phase II studies provide evidence that paclitaxel is active as salvage therapy in patients with several advanced or metastatic tumor types, including NSCLC, ovarian, breast, and head and neck cancers. The response rates achieved in these tumors are particularly impressive because heavily pretreated patients, and those who are refractory to prior standard chemotherapy, have had a high rate of objective responses to paclitaxel. Ongoing studies should define clearly the role of paclitaxel in ovarian cancer. The role of this agent in breast cancer will be defined when the optimal use of paclitaxel in combination with other drugs is determined. In other cancers, including NSCLC and head and neck cancer, future studies will use combinations of cisplatin and paclitaxel. Use of paclitaxel also is being investigated in bladder, esophageal, and stomach cancers, as well as pediatric malignancies, including leukemias and solid tumors. It will be important to determine if there is a dose-response relationship in the range of dosages currently used clinically. Important unresolved issues in the development of paclitaxel include its role in primary therapy of solid tumors, the optimal length of its infusion, a clearer understanding of the toxicities associated with paclitaxel and the development of methods to prevent or minimize these toxicities, and the efficacy and safety of paclitaxel in combination with other agents.