This paper presents a new method to allocate active and reactive losses simultaneously to generators and loads. The allocation is calculated for each transmission branch, identifying and quantifying the buses' responsibilities in losses. This is a two-step process. In the first step, generators are modeled as current injections and loads as constant admittances in order to determine generator participations in losses. In the second step, loads are modeled as current sources and generators as constant admittances in order to determine load participations in losses. The Aumann-Shapley and circuit theories are used to calculate the participation of each real and imaginary current component, considering them as independent players in the complex losses allocation game. The properties of the Aumann-Shapley method ensure equitable allocation and recovery of the total active and reactive losses. Counter-flow, cross-subsidy, and negative allocation issues are discussed. Numerical results are presented and discussed to demonstrate the applicability of the proposed method. © 2006 IEEE.