Computer-assisted telephone interviewing (CATI) employs interactive computing systems to assist interviewers and their supervisors in performing the basic data collection tasks of telephone interviewing. This is the first of a two-paper series presenting an overview of the status of CATI, based primarily on published articles and unpublished reports describing the development of CATI, and experiences with CATI, in the U.S. and other developed nations. This first paper provides a definition of CATI, reviews its history as an applied technology, and examines current evidence (both summary impressions and quantitative data) on CATI's impact on the costs and timeliness of survey data collection.