The Southwest Oncology Group is a major multi-disease, multi-disciplinary, multi-institution group engaged in cooperative cancer research. This organization now consists of 35 Member Institutions, 29 Community Clinical Oncology Programs (CCOPs), 230 Affiliates, and 26 Urologic Cancer Outreach Programs (UCOPs), who together accrue 5,000 patients to clinical trials each year. Currently there are 96 studies open for accrual in 14 committees. The Statistical Center is essential to the design, conduct, and analysis of the cancer research in the Southwest Oncology Group. Its main functions are: (1) to participate in the review of proposed protocols, particularly as regards experimental design, sample size, and feasibility;(2) to provide for registration of all patients on all studies, and for randomization where appropriate;(3) to develop Web and software technology for paperless submission of data;(4) to provide for review and quality control of data collected during studies;(5) to provide for data entry and for computer processing and storage and retrieval of data;(6) to work with the Group chair and other investigators in the Group to improve the quality of clinical trials through improved forms, more uniform and reproducible data definitions, and more economical flow of data;(7) to assist the Group chair in the administration of the Group;(8) to analyze and publish the results of studies in conjunction with the study coordinators;(9) to use the data collected to try to find new leads regarding prognostic factors and late effects;(10) to perform statistical research on the efficient design, conduct, and analysis of cancer clinical trials and cancer control research;and (11) to educate investigators, nurse oncologists and CRAs in statistical analysis, research design and the utilization of the most advanced scientific and data management strategies.