In this chapter, we examine the research literature on question order effects. A question order effect occurs when responses to a prior question on a questionnaire affect responses to a subsequent one. Because questionnaire designers have to settle on some ordering of questions, question order effects are always a possibility. This chapter reviews the literature on empirical studies of survey question order effects, their mechanisms, and their moderators. In addition, we provide guidance for questionnaire construction on the basis of the results of these studies. Question order effects are sometimes categorized more generally as context effects because the prior question is thought to provide a context in which to view the subsequent question. Strictly speaking, survey context is broader than question order and can involve instructions, extra materials presented as part of the survey that are not questions (such as pictures or videos), or even the setting in which a survey is administered. A question order effect is a special type of context effect.Three basic kinds of question order effects have been identified : (a) Answers to the subsequent question are affected by having responded to the prior question but not necessarily affected by which response was given on the prior question (an unconditional question order effect), (b) answers to the subsequent question depend on the response given to the prior question (a conditional question order effect), and (c) the correlation between the prior question and the subsequent question changes depending on which is asked first (an associational question order effect).Question order effects can present serious problems when measuring change over time, whether in longitudinal surveys or in repeated cross-sectional surveys, or even when comparing the results of different cross-sectional surveys. Unless the question order is the same for each data collection, it is difficult to know whether change (or its absence) is due to real respondent change or to question order. presented the first extensive review of question order effects primarily in the area of public opinion. They conducted their own studies to replicate and see the extent of question order effects but did not systematically capture the behavioral or psychological dynamics underlying the effects. In general, among survey methodologists before the early to mid-1980s no general framework for understanding and predicting question order effects was widely accepted. The emphasis on psychology and surveys beginning in the early 1980s changed that. For the first time, the cognitive task of the respondent, rather than just the substance of the question, was given serious consideration. Once that breakthrough had been made researchers could develop theories about the types of judgment required by a question and experiments could be designed to manipulate the task demands of the respondent in theoretically derived ways to test hypotheses about the psychology of the survey response process. This information could be fed ba...