US Oncology Holdings, Inc. offers services, resources, and tools for cancer care delivery system in the United States. It operates in four segments: Medical Oncology Services, Cancer Center Services, Pharmaceutical Services, and Research/Other Services. The Medical Oncology Services segment provides practice management services; pharmaceutical services; and data collection and analytical services for use by physicians and their clinical staff, pharmacists, and patients, including analyses of chemotherapy regimens. This segment also offers an oncology-specific electronic medical records system, known as iKnowMed. The Cancer Center Services segment provides cancer center services through its 83 integrated and community-based cancer centers. This segment also manages 17 radiation-only facilities.