This thesis aims to present the possible relationships and implications between the attributes of the Parmenidean Being and important assumptions of Plato s Theory of Ideas. I will explore relationships and implications particularly through the examination of the aporias of participation of sensitive beings in the Ideas, such as carried out in the dialogue Parmenides. To undertake this line of arguments, it is necessary to tackle the theses about Being, presented by Parmenides in his poem, On Nature, analyzing. Above all, it is necessary to investigate what is known as the Way of Truth, specially the fragment 8 of Parmenides poem. Next, I will examine relevant passages of Plato s dialogues, namely those considered relevant for the development of the principal tenets of Plato s Theory of Ideas. Thus, I will briefly go through certain dialogues from Plato s initial phase, as well as some mature dialogues, focusing in more detail on the medium dialogues such as Phaedo and Banquet, in which this theory is established in its more traditional format. I will also seek to examine the terminology associated with the Idea in these dialogues, so that, in the end, a relationship is established between the criticism of the Parmenides dialogue with the theses presented in Parmenides poem.