Patients with stage IV colorectal carcinoma, other refractory carcinomas, or metastatic adenocarcinomas of unknown primary site receive the above 12-week block of chemotherapy (irinotecan, fluorouracil, and leucovorin calcium) with pelvic irradiation (if indicated). Pelvic irradiation patients with an unresected primary tumor undergo exploratory surgery 4-5 weeks after completion of radiotherapy, even in the absence of visible tumor regression. Radical resection is attempted to effect local control and control of long term symptoms related to the primary tumor. Patients with complete response (CR) or partial response (PR) after both chemotherapy and surgery repeat the above 12-week block of chemotherapy 3 times over 1 year in the absence of disease progression or unacceptable toxicity. Patients with CR or PR after chemotherapy but no response after surgery receive irinotecan IV over 1 hour on days 1-5 and days 8-12 every 3 weeks for 1 year in the absence of disease progression or unacceptable toxicity. Patients with stable disease (SD) or progressive disease after 2 courses of irinotecan and SD, CR, or PR after surgery receive leucovorin calcium and fluorouracil as above every 3 weeks for 1 year in the absence of disease progression or unacceptable toxicity.