The SCCS is a landmark study of racial disparities in cancer incidence and mortality, as well as of disparities in the occurrence of other chronic diseases such as diabetes, hypertension and heart disease. The data collected in this study are available for use to both SCCS investigators and their non-SCCS investigator collaborators. As with all carefully conducted studies, quality control measures applied to the raw data, to the analytic procedures performed on the data, to the use of stored biosamples, and to the resulting scientific manuscripts are essential in order to maintain the integrity of the study. In addition, the collection of ancillary data using study participants is an activity that is encouraged, but must be done in close coordination with primary SCCS operations to ensure the validity and success of such an ancillary study, and to minimize the burden on participants.