To determine whether cancer patients with fever and neutropenia differ in their medical stability, 261 medical records of 184 cancer patients who were hospitalized with fever and neutropenia and treated with conventional antibiotic therapy were studied to determine whether their presenting clinical characteristics influenced the likelihood of subsequent clinical events thought to require urgent medical attention. Overall, serious medical complications, including those without an obvious relationship to infection, occurred in 56 patient courses (21%). We distinguished three clinically determined subgroups of our study population at significantly higher risk than the remaining patient group, which seemed to be at low risk. Major complications occurred in 34 (34%) of 101 inpatients, 12 (55%) of 22 outpatients with concurrent comorbidity requiring inpatient care, and eight (31%) of 26 outpatients without concurrent comorbidity requiring inpatient care but with uncontrolled cancer. However, the remaining patients, who presented as outpatients without significant comorbidity or uncontrolled cancer, had major complications in only 2% of 112 hospitalizations. These results suggest that it may be possible to assess the medical stability of patients with fever and neutropenia based on presenting clinical features. If confirmed prospectively, these results may enable clinicians to identify groups of medically stable patients for whom conventional supportive care, including appropriately administered antibiotics, may be given safely under medical supervision of less intensity or of shorter duration than conventional treatment in the acute-care hospital setting.