Patients with newly diagnosed cancer responsible for organ failures may require intensive care unit (ICU) admission and immediate chemotherapy. Outcomes in this population have not been studied. Prospective observational cohort study. Teaching hospital. All patients admitted to the ICU, from January 1997 to June 2003, for organ failures due to newly diagnosed, untreated cancer and deemed necessary to receive immediate cancer chemotherapy. None. For the period of 6.5 yrs, 100 patients met the study criteria: 43 had acute leukemia, 37 lymphoma, and 12 solid tumors. Median Simplified Acute Physiology Score II was 39 (30-48) points, and median Logistic Organ Dysfunction score was 5 (3-7) points. Three variables were independently associated with 30-day mortality: need for vasopressor therapy (odds ratio, 6.01; 95% confidence interval, 1.86-19.4), mechanical ventilation (odds ratio, 6.36; 95% confidence interval, 1.76-22.94); and hepatic failure (odds ratio, 7.76; 95% confidence interval, 1.25-48.27). Overall survival was 60% after 30 days and 49% after 180 days. Mortality was chiefly dependent on the nature and number of organ failures, not on the nature or stage of the malignancy. The 30-day and 180-day survival rates indicate that, in this selected group of patients, advanced disease at cancer diagnosis should not lead to refusal of ICU admission. Moreover, administration of chemotherapy in the intensive care unit is feasible, and although the mortality rate is high, routine ICU admission of patients with newly diagnosed cancer, specific organ failure, and the need for administration of chemotherapy in the ICU deserves evaluation.