OUTLINE: This is a dose-escalation study of raltitrexed. Patients receive raltitrexed IV over 15 minutes followed 24 hours later by fluorouracil IV. Treatment continues every 3 weeks in the absence of disease progression or unacceptable toxicity. Cohorts of 3-6 patients receive escalating doses of raltitrexed until the maximum tolerated dose (MTD) is determined. The MTD is defined as the dose immediately preceding that at which 2 of 6 patients experience dose-limiting toxicity. An additional 6-10 patients are treated at the MTD. Patients are followed for 6 weeks.