Despite the unassailable claim of Ogilvie and Richmond that “the Agricola is a biography,” chapters 10-38 of Tacitus’ work have been equated by almost every modern commentator with another literary genre, that of history. This paper argues that these chapters are in fact more closely allied with a related, but quite distinct Roman literary genre: commentarii, whose implicit standards had been set more than a century earlier by Caesar’s masterful Gallic Wars. Tacitus’ account of Agricola’s legation to Britain is organized in a closely similar fashion: each of his seven years there is treated by Tacitus quite independently of the others, and the events related are almost wholly restricted to the campaigning seasons. Those specific features of Tacitus’ account which to scholars have suggested history–the geographic/ethnographic digression of 10-13, the paired speeches of Calgacus and Agricola at 30-34, even the author’s partiality in these chapters to the historical infinitive–all have recognizable parallels in Caesar’s commentaries. Recognition of Agricola 10-38 as commentarii rather than as history means that they can no longer be seen unproblematically as an historian’s first steps, a sort of dry run for the author’s ultimate calling, but rather as Tacitus’ attempt to master what was traditionally held to be the raw material of history proper, and to provide for his father-in-law the customary monument of Roman dignitas which he himself could not.