The aim of this single-arm, phase II study was to estimate the tumor response rate and safety profile of erlotinib HCl (erlotinib, Tarceva, OSI-774) monotherapy in patients with refractory, recurrent, HER1/EGFR-positive epithelial ovarian tumors, who had failed prior taxane and/or platinum-based chemotherapy. Thirty-four patients received 150 mg erlotinib orally once daily for up to 48 weeks or until disease progression or dose-limiting toxicity. Two patients had partial responses, lasting 8+ and 17 weeks, giving an objective response rate of 6% (95% confidence interval [CI], 0.7-19.7%). Fifteen patients (44%) had stable disease, and 17 patients (50%) had progressive disease. Median overall survival was 8 months (95% CI, 5.7-12.7 months), with a 1-year survival rate of 35.3% (95% CI, 19.8-53.5%). Patients with rash survived significantly longer than those without (P= 0.009), correlating with rash grade. Erlotinib was generally well tolerated. The most frequent erlotinib-related adverse events were rash (68%) and diarrhea (38%). Erlotinib had marginal activity but was generally well tolerated. The safety profile appears more favorable than typically experienced with standard chemotherapeutic agents, which is encouraging in these heavily pretreated patients. Combination of erlotinib with chemotherapy or other targeted agents should be considered.