The first week, each patient will receive a single dose of 5-FU given by 24 hour continuous IV infusion at its recommended Phase II dose with low-dose oral LV. In the third week, the patient will begin 776C85 (GW776) and LV PO on days 1, 2, 3 at fixed doses. Oral 5-FU will be given on day 2, and the dose will be escalated in successive cohorts of patients. Treatment will be repeated weekly for three weeks, followed by a one week break. The dose of 5-FU will be adjusted according to individual tolerance. Cohorts of three patients will be entered at each dose level of 5-FU, which will be escalated until dose-limiting toxicity is seen (guidelines are outlined in the following schema). Treatment will be continued indefinitely until evidence of disease progression, provided the patient is tolerating therapy and wishes to continue.