Background: Doxorubicin and pemetrexed have both shown single-agent activity in breast cancer. Preclinical and clinical evidence indicates that a combination of the 2 agents might have an additive or synergistic effect. A phase II trial was initiated to assess the antitumor activity and safety of pemetrexed plus doxorubicin in women with advanced breast cancer. Patients and Methods: Anthracycline-naive patients with advanced breast cancer received doxorubicin 50 mg/m2 plus pemetrexed 500 mg/m2 (both intravenously) on day 1 of 21-day cycles, as first-line therapy, with standard vitamin supplementation. Seventy-nine women were enrolled (median age, 55.3 years). Seventy-six patients (96.2%) had an Eastern Cooperative Oncology Group performance status of ≤ 1. Results: At baseline, 35 patients (44.3%) had visceral metastases. Three (4.2%) patients were HER2/neu positive, and 30 (42.3%) patients were HER2/neu negative. The objective response rate was 55.7% (95% exact CI, 44.1%-66.9%), including 2 (2.5%) complete responses. Median progression-free survival was 8 months (95% CI, 6.5-13.3 months). Twoyear survival rate was 61.7% (95% CI, 49.7%-71.6%). Grade 3/4 drug-related toxicities in ≥ 10% patients included neutropenia (24.1%) and leukopenia (10.1%). Conclusion: In patients with advanced breast cancer, the combination of doxorubicin plus pemetrexed was well tolerated and showed promising antitumor activity that warrants further study.