ABSTRACT
I. INTRODUCTION
The case-control or retrospective study is one of the most important tools currently available to the chronic disease epidemiologist for investigation of cancer etiology. New cases of a particular site and/or type of cancer occurring in a defined population are compared to a control sample with respect to genetic markers, exposure to environmental agents, and other suspected risk factors. The advantages of this study design are that a relatively large number of cases may be ascertained in a short period of time and that information may be collected simultaneously on a variety of nuisance factors which may confound the association of primary interest. Disadvantages relate to the accuracy of the exposure histories, which must usually be obtained by interview or other retrospective means, and to questions of bias in the selection of the control sample.
