The association between glutathione S-transferase pi (GSTpi) and other clinicopathological parameters, response to chemotherapy and clinical outcome were investigated in chemotherapy naive epithelial ovarian cancer patients. Paraffin-embedded material from 55 patients were used for immunohistochemical analysis. All patients had received six cycles of cisplatinum-based chemotherapy and 41 of them were revalued by laparotomy. Pre- and post-chemotherapy GSTpi staining were detected in the cancer tissues of 18/55 (32.7%) and 5/14 (35.7%) patients, respectively. GSTpi expression was not associated with other clinicopathologic parameters. Of 17 patients with postoperative measurable residual disease clinical response was observed in 4/7 of GSTpi positive and in 9/10 GSTpi negative patients (p = 0.25). Pathologic complete response (pCR) was achieved in 5/8 of GSTpi positive and 11/22 of GSTpi negative cases (p = 0.69). There was no significant difference in overall survival and progression-free survival (PFS) according to initial GSTpi status. However the PFS of the five patients (median 22 +/- 5.9 months) who had postchemotherapy positive GSTpi was significantly shorter than the nine patients (10.0 +/- 2.19 months) who had negative GSTpi (p = 0.006). This difference was not observed in overall survival. These results suggest that initial immunohistochemical staining of GSTpi does not aid in the prediction of pCR and clinical outcome in patients with epithelial ovarian cancer. Nonetheless investigation of GSTpi expression after chemotherapy needs further evaluation.