The oldest and most important of the Commentaries on the Tipitaka, brought, according to tradition, to Ceylon by Mahinda, who translated it into Singhalese (Cv.xxxvii.228f). It thus came to be called the Síhalatthakathá. Besides exegetical material on the Páli Canon, it contained also historical materials on which were later based the Páli Chronicles, the Mahávamsa and the Dípavamsa. For a description see Geiger's Dipavamsa and Mahavamsa, pp. 44, 63, etc.
The Mahá-atthakathá was the chief source from which Buddhaghosa drew his materials for his Commentaries and is often referred to in his works, particularly in the Samantapásádiká. E.g., Sp.i.2; ii.494; 265; iii.537, 616, 617, 627, 701, 716, 718, 726; iv. 744, 776, 783, 817, 863, 914, 923; DhSA.157; DA.i.180, etc.
The Mahá-atthakathá was in charge of the monks of the Mahávihára at Anurádhapura. It was superseded by the Commentaries of Buddhaghosa, Dhammapála and others, and is not now extant. It is often referred to merely as Atthakathá. E.g., VibhA.56, 155, 200, etc.