The aim of this dissertation is to evaluate the contribution and the development of the English School of International Relations. In order to achieve this, the analytical axis will be historic, emphasising a chronological approach. In this sense, it was accessed the contribution of two of its leading theorists: Martin Wight and Hedley Bull, that together established the mains theoretical and conceptual axis constitutive of the school. In the second part, the debate about the identity and the validity of the contribution of the school in the 1980s was analysed. In the last part, it is offered an evaluation of the English School in the 1990s. Its bifurcation into two approaches, a critical and a classical one; and the theoretical innovation brought by a new generation of theorists, will be introduced. Latter on, it will be offered an critical analysis of the debate that took place in the English School after the conflict at Kosovo.