This is the third in a series of 3 article on questionnaire research in which the authors aim to present a practical guide for producing questionnaire research that is well designed, well managed, & non-discriminatory & which contributes to a generalizable evidence base. In this article, the authors consider how to overcome the problems with accessing disempowered & socially excluded groups, cross cultural issues, & participants whose physical or mental health may interfere with their ability to complete a questionnaire. They also discuss the training & support of researcher staff. (21 refs)