 Rationale: Patients with advanced stage head and neck cancer, especially those with disease in the hypopharynx, oropharynx, or oral cavity, and poor performance status defined through clinical testing, are often not eligible for clinical trials and treated with best supportive care. The possibility of developing a well-tolerated chemotherapy regimen in these patients may lead to an equivalent benefit and better palliation. The current study offers the chemotherapy drug pemetrexed to patients with advanced head and neck cancer. Researchers consider this agent to have some anti-tumor efficacy against a variety of site-specific cancers, including head and neck cancer with a response rate that is similar to other single chemotherapy drugs. In addition, previous research indicates that toxicities associated with pemetrexed have been reduced when patients are given folic acid and B12 vitamin supplementation. Along with pemetrexed, the current study provides study participants with both folic acid and B12. 