BACKGROUND While ovarian cancer is one of the most sensitive cancers to cytotoxic drugs, with objective response rates of 60-80% routinely being reported in previously untreated patients, the majority of individuals with advanced disease ultimately relapse. Paclitaxel, a new and novel antimicrotubule agent, has shown activity as a salvage therapy in epithelial ovarian cancer. More importantly, in a prior study, it has been shown to be active in tumors that have displayed resistance to platinum compounds, with a reported response rate of 20%. Ifosfamide has shown activity in the treatment of patients who previously demonstrated clinical resistance to a platinum-cyclophosphamide combination. Recently, a synergistic activity of Taxol combined with ifosfamide has been reported in ovarian cell lines. Based on these data, a phase I/II study of a combination treatment with paclitaxel and ifosfamide was performed. METHODS Thirty-one patients with recurrent ovarian cancer or ovarian cancer refractory to cisplatin (CDDP)-containing regimens were treated with paclitaxel at a dose of 135 mg/m2 on day 1; ifosfamide was administered at 1 g/m2 on days 2 and 3 for the first cycle and 1.5 and 2 g/m2 with the same schedule in cycles 2 and 3, respectively. In the absence of toxicity, the dose of ifosfamide was maintained at 2 g/m2 for the last three cycles. Cytotoxic therapy was repeated every 3 weeks. RESULTS A 30% overall objective response rate was achieved in the 30 patients assessable for response. Among 21 platinum-resistant patients, 4 partial responses (19%) were observed, while in the 9 platinum-sensitive patients 2 complete responses and 3 partial responses (55%) were observed. Myelosuppression was the predominant toxicity. Leukopenia (WHO grade 3-4) occurred in 10% of patients who received ifosfamide at a dose of 1 g/m2 and in 18% of patients treated with ifosfamide at 1.5 g/m2. CONCLUSIONS Our results confirmed a low activity of paclitaxel in platinum-resistant patients. The results of this combination treatment with paclitaxel-ifosfamide in our platinum-sensitive patients support further investigations in a randomized study of the combination regimen against paclitaxel alone or retreatment with organoplatinum compounds.