This chapter addresses a major question regarding survey research—why do people agree to participate. We present a framework for explaining survey response. This framework has various stages, and is applicable to all modes of data collection—mail, personal interview, telephone, and web. Next, we discuss six theories from the literature that have been used—to a greater or lesser extent—to explain survey response behavior. Such theories have been applied to the appeals to participate and to overall research design and technique that would encourage and facilitate respondent completion and submissions. Specific data collection techniques that can have an effect on response quantity and quality are then discussed briefly (these topics are discussed elsewhere in this book). Finally, the matter of effect of topic is presented. Both interest in topic and sensitivity of topic have potential impacts on response rate and data quality.