There is a strong tradition of quantitative research in the health sciences, but qualitative research designs are now being used more frequently to investigate certain areas of rehabilitation, such as patients' views of health care services, and how clinicians make decisions during evaluations and treatment. Many qualitative approaches are available for conducting these types of inquiries, such as interviews, participant observation, and focus groups. Focus groups are unique because they combine interviewing, participant observation, and group interaction. Focus groups are therefore particularly useful when the researcher wants to investigate people's thoughts because the interaction between participants can elicit data and ideas that might not be uncovered in one-on-one questioning. To optimize the data obtained from focus groups, careful attention must be paid to the composition and number of groups, as well as the selection and training of the moderator, and the development of the question route. This article will review these components of focus group research design, as well as highlight other important considerations for planning and conducting focus groups. Issues specific to analysis and trustworthiness of focus group data will be addressed in Part 2.