A phase II study of piritrexim in combination with methotrexate in recurrent and metastatic head and neck cancer. Thirty patients with recurrent and/or metastatic head and neck cancer were treated with sequentially administered methotrexate (MTX) and piritrexim (PTX). The treatment schedule consisted of intravenous (IV) MTX (50 mg/m2) administered on day 1 and oral PTX (75 mg/m2) administered twice daily on days 8 to 12. Courses were repeated every 21 days with dose escalation in subsequent courses aimed at achieving Grade 1 toxicity. Two patients were not evaluable for response, 5 (17%; 95% confidence interval, 4% to 30%) had a partial response (PR), 10 had stable disease, and 13 had progressive disease. All five responses were seen in patients with regional lymph nodes as measurable disease. The median time to progression for all patients was 1.4 months, and the median survival was 6.7 months. Generally, this regimen was well tolerated with only mild toxicity seen during cycle 1 in the majority of patients. Dose escalation in subsequent cycles was possible in a high percentage of patients. Although the overall response rate and survival figures in this Phase II trial were disappointing, the doses and schedule used in this trial may have been suboptimal as reflected by the low incidence of moderate to severe toxicity. Additional evaluation of this combination of drugs in a more aggressive schedule may be warranted. 