The volume of scholarly literature on Aeschylus is already so large that an attempt to make even the minutest addition to it may well appear rash. But the standard literature has most often dealt with the dramatic technique of Aeschylus and with the moral or social issues raised by him. This is true even of Kitto's work, Form and Meaning in Drama. Thus, in his preface, he states, ‘The presumption with Aeschylus, Sophocles and Shakespeare, when he wrote Hamlet, is that the dramatist was competent. If the dramatist had something to say and if he was a competent artist, the presumption is that he has said it and that we, by looking at the form which he has created, can find out what it is’; that is to say, he was thinking of dramatic form. This article is concerned with an aspect of form which does not appear to have received sufficient attention. I would call it the ‘poetic’ aspect of form. ‘Poetry’ is not easy to define, but one of the ‘tentative formulas’ given by Lattimore expresses what I mean. ‘What is directed’, he said, ‘neither to the emotion nor the intellect but to the imagination is the poetry of the plays.’ Aeschylus is a poet even more than he is a dramatic artist. One would naturally, therefore, expect to find in his plays much of the stuff that is directed towards the imagination. This ‘poetic’ element is to a large extent communicated through the form, which will enhance his meaning or will even be an image of his thought. It is from this point of view that I propose, in this note, to examine the Oresteia, in the hope that it may throw some light on many of the peculiarities of construction that are so prominent a feature of the trilogy.