Computer-assisted telephone interviewing systems have made conducting surveys a more dynamic process. Data collection procedures can now respond not only to the needs of the investigator, out to the observations made during the survey itself. These observations include both the substantive matters and the respondents' behavior with regard to participation in the survey. Survey designs may then become more fluid, with their ultimate design the result of a series of decisions that will be made during the course of the survey, based on the goals of the survey and on the nature of the cumulative findings. The role of the interviewer continues to be key, but computer-assisted interviewing systems serve to simplify the clerical aspects of the interviewer's work, making it possible for the interviewer to concentrate on his or her major assignment to establish and maintain the respondent co-operation.