To examine the magnitude of out-of-pocket expenditures for patients undergoing chemotherapy in an outpatient clinic.Cross-sectional survey.An urban outpatient chemotherapy clinic.Convenience sample of 20 adult patients with cancer.Birenbaum's Cost Interview Schedule was administered to patients as they awaited treatment in the chemotherapy clinic; demographic data were collected from patients' charts.Out-of-pocket expenditures incurred during a one-month period of chemotherapy treatment.Estimated out-of-pocket expenses, excluding lost income, ranged widely from $12-$3,130.Out-of-pocket expenses come from multiple sources over time and can be more costly than previously recognized. Extent of out-of-pocket expenditures may depend on treatment protocol, ease of symptom management, functional status, and nonclinical elements such as socioeconomic factors. Additional investigation can identify which patients are most vulnerable to excessive out-of-pocket expenses and who may be at risk for treatment delay or withdrawal because of difficulties in meeting expenses.Recognition of the hidden costs incurred by patients with cancer as they undergo treatment enables nurses to anticipate the financial burden of illness, make necessary referrals, address quality-of-life issues because of financial distress, and avert critical delays in treatment related to overwhelming healthcare costs.