ABSTRACT Survey data are compromised when respondents do not interpret questions in the way researchers expect. Cognitive interviews are used to detect problems respondents have in understanding survey instructions and items, and in formulating answers. This paper describes methods for conducting cognitive interviews and describes the processes and lessons learned with an illustrative case study. The case study used cognitive interviews to elicit respondents' understanding and perceptions of the format, instructions, items, and responses that make up the Diabetes Symptom Self-Care Inventory (DSSCI), a questionnaire designed to measure Mexican Americans' symptoms of type 2 diabetes and their symptom management strategies. Responses to cognitive interviews formed the basis for revisions in the format, instructions, items, and translation of the DSSCI. All those who develop and revise surveys are urged to incorporate cognitive interviews into their instrumentation methods so that they may produce more reliable and valid measurements.