There is a dearth of information for pediatricians to use in choosing questionnaires that would be useful in medical practice. In this article, general guidelines are presented for primary child health clinicians to use in selecting questionnaires. Concepts such as reliability, validity, readability, response format, scoring and completion time, and norms are reviewed, and the implications of these concepts for practitioners are discussed. Guidelines are applied to selected behavioral questionnaires to illustrate their importance.