Bachelor, St. Mary of Lake Seminary, Mundelein, Illinois, 1951. Licentiate of Sacred Theology, Pontifical Gregorian University, Rome, 1955. History Eccl.D., Pontifical Gregorian University, Rome, 1962.
Doctor of Humane Letters (honorary), Belmont Abbey College, 1992.
Faculty Catholic University American, Washington, 1959-2000, professor church history, 1975-2000, Kelly-Quinn distinguished professor church history, 1999-2000, professor emeritus church history, since 2000. Expert 2d Vatican Council, 1962-1965. President American subcommittee International Commission Comparative Church History, 1978-1980, assesseur, 1980—2010.
Member subcommittee National Conference Catholic Bishops, 1966-1976, 87-92. Member Pontifical Committee History Sciences, 1982—2009. Honorary member Accademia di San Carlo (Milan), since 1986.
Honorary prelate (monsignor), 1992. Protonotary Apostolic Supranumerary, 2005. Member International Joint Commission for Theological Dialogue between Catholic Church and Orthodox Church, 1999-2006.
Member Anglican-Roman Catholic Consultation in the United States, 2002-2007. Member advisory committee Association Friends of the Archives of Congregation for Doctrine of the Faith (Holy See), since 1999.
Member American History Association, American Society Church History (county 1980-1982), American Cath.Hist. Association (executive secretary since 1961, secretary, treasurer since 1983), Catholic Commision on Intellectual and Cultural Affairs.