In 1989 the National Cancer Institute funded the second round of Data-Based Intervention Research (DBIR) cooperative agreements with state health agencies to implement a four-phase cancer prevention and control planning model that would establish ongoing cancer prevention and control programs. Activities included identifying and analyzing relevant data to develop a state cancer control plan. The authors reviewed the data analysis and planning activities of five DBIR projects to understand: how states use different types of available data to make public health planning decisions, in what ways available data were sufficient or insufficient for this planning, and perceived costs and benefits of a data-based planning approach. Many of the sources of and ways in which health statistics and behavioral data were used were consistent across states. Sources and use of data on the availability and utilization of health services and on cancer control policies were less consistent. Data were most useful in making decisions to address specific cancers, to target populations or regions, to identify general barriers, and to influence policy makers and the public. Data were less influential in identifying specific barriers within target populations and determining what proven intervention components should be implemented and how. The process of pulling this information together and involving working groups and coalitions was considered very beneficial in establishing the credibility of the state health agency in addressing the state's cancer problem. This process relied on a national infrastructure that provided financial resources, sources of data, and research results.