This article presents an interview with Dr. John Bissell Carroll, who was considered by many to be the premier psychologist in the 20th century in terms of contributions to educational linguistics. In retrospect, this occasion has very special significance, as it was one of the last interviews that Dr. Carroll granted near the end of his illustrious career. Dr. Carroll was lead developer of the Modern Language Aptitude Test (MLAT). The MLAT has been used for selection, placement, and guidance by schools and U.S. government agencies for more than 40 years, and Dr. Carroll's associated research and writings on language aptitude are widely considered the most comprehensive and authoritative treatment of the subject even today. Yet, not all of the story behind the MLAT has been previously recorded. One of the main purposes of this interview was to augment the documentation of this important part of language testing history. (Contains 11 footnotes.)