János Szentmihályi became a librarian upon a forced decision. He learnt the profession as an adult, and was interested mostly in the theoretical and methodological aspects of bibliograhy and information services. He was also a lecturer in these subjects at the university. His main fields of research were: the concept of bibliographies, the evaluation of bibliographies, problems of the national bibliography and that of Hungarica bibliographies. He was the first in Hungarian literature to survey and classify social science bibliographies, and Hungarika Külföldi Folyóiratszemle, started in 1971, and from 1976 on Hungarika irodalmi Szemle were compiled according to his conception.