Editor,—In the recent editorial by Bates and Rogstad¹ the authors describe the problems associated with conducting postal research including response rates, use of incentives, bias, mailing clinical specimens, and ethical issues. We would like to add that there are other important issues to consider when undertaking questionnaire research.

The effectiveness of incentives to increase response rates remains controversial. Kalantar and Talley² recommend using a lottery incentive as it increases response rates after the first mailing. However, differences between groups were not large, and decreased during follow up and disappeared by the fourth mailing. Koloski et al³ found that the use of lottery tickets increase response rates, but may be limited when using them with long questionnaires (32 pages). Moreover, they compared …