Publisher Summary The primary goal of this chapter is to promote an awareness of the scope and breadth of the scientific discipline underlying questionnaire and survey development that should guide the design and analysis phases of the research study. The following study presents measurement, design, and analysis issues with which all clinical investigators should be familiar prior to employing patient surveys and questionnaires in their research studies. Observing or asking patients how they feel and function can also obtain certain types of information required for testing clinical research hypotheses. For many areas of clinical investigation the interpretation of research results derived solely from clinical and laboratory data can be enhanced by information that reflects the patient's perspective of a disease condition or state of health. In particular, studies evaluating the risks and benefits of new therapies should always include a description of benefits from the patient's perspective. The purpose of this chapter is to describe the scientific framework, as well as the more commonly used methodological issues and techniques, for collecting data from clinical research subjects using questionnaires and surveys. The use of questionnaires and survey instruments can greatly expand the types of data that can be obtained from clinical research. The purpose of a questionnaire is to better understand how patients feel and behave as a group, usually after some form of intervention or therapy.