The National Institutes of Health recently established a large cancer day hospital (CDH) to address the need to support new research initiatives in the face of a shrinking research budget. By design, the CDH is very much a nursing unit. It employs a collaborative practice model of patient care delivery that emphasizes the nurses' independent clinical- and protocol-related responsibilities and roles. The CDH is designed to be budget neutral. An increased outpatient throughput and a decrease in inpatient days for at least one large protocol population (patients receiving therapy for prostate cancer) have been demonstrated. With a steadily increasing number of patients, the CDH appears to be a well-accepted and cost-effective site for the care of patients enrolled in oncology clinical trials.