The authors assess the activity and toxicity of paclitaxel in previously untreated patients with multiple myeloma. Eighteen patients with previously untreated multiple myeloma were enrolled. Paclitaxel was given in a dose of 250 mg/m2 by a continuous intravenous infusion for 24 hours every 21 days for four cycles. All patients received granulocyte colony stimulating factor in a dose of 5 microg/kg each day until the absolute neutrophil count was 10,000/mm3. All patients were evaluated after four cycles. Four (29%) objective responses were observed in the 14 eligible patients. No complete responses occurred. Three lethal toxicities were observed, two were the result of neutropenic sepsis. Sixty-one percent of patients experienced some type of severe nonhematologic toxicity. Patients who received four cycles of paclitaxel were given further treatment at the discretion of the investigator. The median survival of all eligible patients was 2.8 years, which is comparable with the median survival with melphalan and prednisone of 2.3 years or vincristine, carmustine, melphalan, cylophosphamide, and prednisone of 2.4 years. Paclitaxel in the dosage used in this study has prohibitive toxicity. The four (29%) responses in 14 evaluable untreated patients indicates that paclitaxel is active in the treatment of multiple myeloma. No complete remissions were recorded. Further studies using paclitaxel in a smaller dose, in combination with other agents, or using one of the paclitaxel analogs may be useful in the treatment of multiple myeloma.