OUTLINE: This is a dose escalation study of SCH 66336. Patients receive oral SCH 66336 twice daily for 56 days. Patients receive leucovorin calcium IV over 1-2 minutes immediately followed by fluorouracil IV over 1-2 minutes on days 1, 8, 15, 22, 29, and 36. Courses repeat every 56 days in the absence of disease progression or unacceptable toxicity. Cohorts of 3-6 patients receive escalating doses of SCH 66336. The maximum tolerated dose is defined as the dose at which no more than 1 of 6 patients experiences dose limiting toxicity (DLT) during course 1, with at least 2 patients experiencing DLT at the next higher level.