For a hundred years, ancient historians have been seeking to determine the date at which Caesar's Gallic command legally expired—a date which, curiously, no ancient writer has troubled to record. Little has been added, save repetition, to the arguments used by Mommsen in favour of 1st March, 49 B.C., by Zumpt in favour of 13th November, 50 B.C., and by Hirschfeld in favour of 1st March, 50 B.C. A few ‘freaks’ have sprouted, 29th December, 50 B.C., from Judeich, and an uncertain date between 31st July and early October, 50 B.C., from Stevens. And now, instead of offering a strange or even a familiar device for untying the Gordian knot, I want to suggest that it should be cut; that there was no exact terminal date for Caesar's tenure of his command. This I can only do by challenging what most scholars are content to accept, the foundations on which Mommsen placed his own discussion of the problem. Before I proceed to the problem itself, I hope to establish, in order, the following three points : (1) that Sulla did not, as Mommsen thought, make a clean severance between magisterial office and provincial government; (2) that it was not in the nature of long-term commands under the Republic to have a specific terminal date ; and (3) that sections 36 f. of Cicero's De provinciis consularibus do not supply incontrovertible evidence for certain facts and constitutional principles, for which their evidence is often assumed to be authoritative.