The controversy regarding the treaties between Rome and Carthage is almost as ancient as the Punic Wars themselves, and unlike these it has not the merit of having come to an end. Strangely enough, the battle of dissertations has chiefly raged round a point of minor importance, and the key position has been the scene of nothing more than some desultory skirmishing. The question whether the first treaty between Rome and Carthage was contracted in 509 B.C. or in 348 B.C. has little or no bearing on the history of the Punic Wars. On the other hand, our judgment on the rights and wrongs of these wars must turn largely on the question whether at the outbreak of the first war there was a treaty in force which bound the Carthaginians not to interfere in Italy, and the Romans not to interfere in Sicily. This latter question was raised in the age of the Punic Wars themselves by the Greek historian Philinus, who argued that the Roman occupation of Messana was a breach of the aforesaid treaty. And the importance of this contention was realised by Polybius, who seized upon Philinus' accusation in order to polemise against it. But the success of Polybius' apparent refutation of Philinus has been so complete that the treaty invoked by Philinus has been generally discredited, and those few modern scholars who have raised the question of the treaty afresh have generally been snubbed for their pains. Nevertheless the point at issue is one which requires to be settled. The present article is an attempt to review the evidence and to make a definite pronouncement upon it.