Strategies for identifying patients at high risk of chemotherapy-induced neutropenia are reviewed. Among lung cancer patients, a 24% rate of neutropenia has been reported. This rate is below the 40% threshold recommended by the American Society of Clinical Oncology (ASCO) for the prophylactic use of colony-stimulating factors. Risk factors for febrile neutropenia in patients receiving adjuvant chemotherapy for breast cancer include older age, fluorouracil-containing regimens, bone marrow involvement or prior myelosuppressive therapy, and concomitant or prior radiation therapy. According to the Silber predictive model, factors suggesting a high risk of hospitalization for febrile neutropenia include the absolute neutrophil count during the neutrophil nadir in cycle 1 of chemotherapy. Patients with non-Hodgkin's lymphoma (NHL) are at risk of febrile neutropenia and fall on the edge of the ASCO guidelines. Risk factors in NHL patients include certain combination chemotherapy regimens, an albumin concentration of > 3.5 g/dL, an above-normal lactate dehydrogenase concentration, bone marrow involvement, age of > 65 years, and renal disease. Patients can be stratified into low-risk and high-risk categories for febrile neutropenia. High risk is associated with a duration of neutropenia of more than seven days and concomitant medical conditions, such as hypotension and diarrhea. A majority of low-risk patients can be managed as outpatients. Prophylactic use of colony-stimulating factors is currently believed not to be cost-effective if the frequency of febrile neutropenia is less than about 20% for a given treatment regimen. Patients at higher risk of febrile neutropenia in association with cancer chemotherapy may include the elderly and those with specific malignancies and prior neutropenic events, as well as those receiving combination chemotherapy and radiation therapy.