Since the first cloning of P2Y receptor sequences in 1993 it has become apparent that this family of G-protein-coupled receptors is omnipresent. At least 25 individual sequences entered in the GenBank sequence database encode P2Y receptors from a variety of species ranging from the little skate Raja erinacea to man. In man, six receptor subtypes have been cloned and found to be functionally active (P2Y₁, P2Y₂, P2Y₄, P2Y₆, P2Y₁₁, and P2Y₁₂). In this article a review of the P2Y receptor subtypes is presented considering both their sequences and the pharmacological profiles of the encoded receptors expressed in heterologous expression systems.