The questionnaire, one of the most frequently used methods in the study of language attitudes, can be used to elicit both qualitative and quantitative data. This chapter focuses on the questionnaire as a means of eliciting quantitative data by means of closed questions. It begins by examining the strengths of doing this (e.g. the fact that the resulting data can easily be compared and analysed across participants) as well as the limitations (e.g. the fact that issues unforeseen by the researcher usually do not come to the fore). The chapter then discusses key issues in research planning and design: for example, question types, question wording, question order, reliability and validity, and more general issues regarding questionnaire design. The chapter also considers questionnaire distribution. The exploration of data analysis and interpretation focuses on data cleaning and coding, statistical analyses, and some points of caution regarding the interpretation of findings from questionnaire-based studies. A case study of language attitudes in Quebec serves to illustrate the main points made in the chapter. The chapter concludes with further important considerations regarding the context-specificity of findings and the benefits of combining questionnaires with other methods of attitude elicitation.