That the Middle Irish poet Gilla Cóemáin was active in the year 1072 has been generally accepted on the strength of a poem attributed to him, in which this is given as the date of composition. The poet does not name himself, however, and the attribution to Gilla Cóemáin appears to depend on a heading in a single medieval copy. This article will examine the evidence afresh, comparing the poem that contains the date with other poems associated with Gilla Cóemáin in terms of metre and of historical doctrine, and attempting to determine whether there are any further indications that speak for or against his authorship.