OUTLINE: This is a dose escalation study of irinotecan and raltitrexed. Patients receive irinotecan IV over 90 minutes on days 1 and 8 followed by raltitrexed IV over 15 minutes on day 1. Treatment repeats every 21 days in the absence of disease progression or unacceptable toxicity. Cohorts of 3-6 patients each receive escalating doses of irinotecan and raltitrexed until the maximum tolerated dose (MTD) is determined. The MTD is defined as the dose preceding that at which 2 of 6 patients experience dose limiting toxicities. Additional cohorts receive raltitrexed on day 2 rather than day 1 near the final dose levels of the combination drugs.