The chief work of Suetonius is his lives of the Caesars which, as it appears, were sometimes distributed in eight books, as they are in some manuscripts. The authorities which he followed for the several lives have beer diligently examined by Augustus Krause (De Suetonii Tranquilli Fontibus et Auctoritate, Berlin, 1841). Krause gives some reasons for supposing that Suetonius consulted the historical writings of Tacitus, and he argues, that as Tacitus did not write his annals before A. D. 117, in which year Hadrian succeeded Trajan, Suetonius did not write the lives of the Caesars before A. D. 120. This is not very satisfactory, though it must be admitted that there are many expressions in Suetonius, which closely resemble the expressions in Tacitus ; and Suetonius, a grammarian (grammaticus), was likely enough to copy particular phrases. Indeed Suetonius often quotes Senatusconsulta and other documentary evidence in the very words, which Tacitus as a general rule did not. These lives of Suetonius are not and do not affect to be historical : they are rather anecdotical. and in the nature of Mémoires pour servir. His authorities are the writings of the Roman emperors themselves and those of their freedmen, Epistolae. Orationes, Testaments, and other documents of that kind; public documents, as Senatusconsulta, Fasti, inscriptions, and the Acta of the Senate and the people; also the Greek and Roman writers on Roman history. He also learned much from conversation with those who were older than himself, and he would know something of Titus and Domitian at least, as he was a young man during their reign. Suetonius does not follow the chronological order in his Lives, but he groups together many things of the same kind, as he says himself (Augustus, 100.9). His language is very brief and precise, sometimes obscure, without any affectation of ornament. He certainly tells a prodigious number of scandalous anecdotes about the Caesars, but there was plenty to tell about them; and if he did not choose to suppress those anecdotes which he believed to be true, that is no imputation on his veracity. As a great collection of facts of all kinds, the work on the Caesars is invaluable for the historian of this period. His judgment and his honesty have both been attacked by some modern critics; but we are of the same opinion as Krause that on both grounds a careful study of his work will justify him. The friendship of the younger Plinius is evidence in favour of the integrity of Suetonius, and Vopiscus, no great authority, it is true, calls him a most accurate and impartial writer (Flav. Vopisc. Firmus, 100.1; compare the Life of Probus, 100.2). Those who attack the credit of Suetonius must conduct the assault with more ability and judgment than H. Heisen in his absurd essay, entitled " Dissertatio de Imperatoria majestate a primis Historiae Augustae conditoribus indignissime habita." (Symbol. Litt. Bremen. tom. i. iii.)

The treatise and that are probably only parts of a larger work, for Hieronymus says in a letter to Desiderius, " I have written a treatise on illustrious men from the time of the Apostles to our own age, imitating therein Tranquillus and the Greek Apollonius." (Casaubon's note on the title of the work De Illustribus Grammaticis.) These two treatises contain a few biographical and other notices, that are occasionally useful.

It has been conjectured that the few scanty lives of the Latin poets, already enumerated, belonged to a larger work De Poetis. If this conjecture be true, the short notice of the elder Plinius may not be by Suetonius, and Casaubon will not allow it to be his. But the opinion as to the book De Poetis is merely a conjecture.

A work entitled , which has been attributed both to Suetonius and the younger Plinius, is now unanimously assigned to Aurelius Victor.

Fragments of Greek works.