John Todd was professor of mathematics at Caltech from 1957 to 1981. This interview in two sessions in March and April of 1996, conducted by Shirley K. Cohen, briefly covers Todd's childhood in Northern Ireland and traces his educational path as an aspiring engineer to Queen's University, Belfast (bachelor's degree, 1931), where he studied mathematics under A. C. Dixon; after Queen's, to Cambridge University as a graduate student (without degree) for two years under J. E. Littlewood. After four further years teaching in Belfast, Todd was hired at King's College, University of London, where he met his wife, the mathematician Olga Taussky, then a postdoc; their marriage in 1938. War work initially involves degaussing of ships for the British navy, then evolves into establishing centralized mathematical computing for the Admiralty. Postwar immigration brings Todds to US, 1947, both to work at US Bureau of Standards; comments on McCarthy era experiences there. John and Olga accept teaching jobs at Caltech, 1957. Note on portrait of Olga, painted in Belfast by mother of crystallographer P. P. Ewald [Clara Ewald, 1939]. Relates story of saving German mathematicians from French-Moroccan troops, 1945, in Oberwolfach in the Black Forest; mathematical institute there survives today. Discussion of teaching computation at Caltech (numerical analysis, numerical algebra, matrix theory); brief mention of mathematical colleagues F. Bohnenblust, A. Erdélyi, M. Ward, and H. P. Robertson. Olga's success as a teacher, although initially barred from professorial ranks. Remarks on state of mathematics and beginnings of computer science at Caltech; mention of student H. H. Hwang.