Studies the historical origins of the periphrastic perfect in its two constructions, the type tá sé tar éis é a dhéanamh (‘after’ perfect) and the tá sé déanta aige (verbal adjective + ag, for which a derivation from a possessive stative formation is sought), and surveys their reflexes in Ulster, Connacht and Munster Irish, Scottish Gaelic, Manx, as well as in Hiberno-English.