He next turned his attention to practical lexicography. His first attempt was the Dictionary of Greek and Roman Antiquities, which appeared in 1842. The greater part of this was written by him. In 1849 followed the Dictionary of Greek and Roman Biography and Mythology, and the Dictionary of Greek and Roman Geography in 1857. In this work some of the leading scholars of the day were associated with him. In 1850 he published the first of the school dictionaries; and in 1853 he began the Principia series, which marked a distinct step in the school teaching of Greek and Latin. Then came the Students' Manuals of History and Literature, in which the Greek history was the editor's own work. In carrying out this task Smith was most ably seconded by John Murray, the publisher, who, when the original publishers of the dictionaries got into difficulties, volunteered to take a share in the undertaking. The most important, perhaps, of the books edited by Smith were those that dealt with ecclesiastical subjects. These were the Dictionary of the Bible (1860–1865); the Dictionary of Christian Antiquities (1875-1880), undertaken in collaboration with Archdeacon Samuel Cheetham; and the Dictionary of Christian Biography (1877–1887), jointly with Dr. Henry Wace. The Atlas, on which Sir George Grove collaborated, appeared in 1875. From 1853 to 1869 Smith was classical examiner to the University of London, and on his retirement he became a member of the Senate. He sat on the Committee to inquire into questions of copyright, and was for several years registrar of the Royal Literary Fund. He edited Gibbon, with Guizot's and Milman's notes, in 1854–1855. In 1867, he became editor of the Quarterly Review, which he directed with marked success until his death; his remarkable memory and accuracy, as well as his tact and courtesy, specially fitting him for such a post. He was DCL of Oxford and Dublin, and the honour of knighthood was conferred on him the year before his death (7 October 1893). He was survived by his wife and brother.