The term mail questionnaire refers to the instrumentation of a self-administered survey that has been laid out and reproduced on a paper-based printed medium with the intention that data collection operations will be implemented via traditional postal service deliveries. A survey researcher's solicitation and collection of data via postal communications that include a mail questionnaire is called a mail (or postal) survey.

In mail surveys, the initial delivery of the mail questionnaire is typically in the form of a survey packet. In addition to the mail questionnaire itself, this packet typically includes a cover letter explaining the purpose of the study and encouraging participation, a postage-paid pre-addressed return envelope, and some form of pre-paid incentive or participation gift intended as a social gesture of appreciation. (A ...