Developing countries are increasinglypursuing and benefitting from regional power systemintegration (RPSI) as an important strategy to help providereliable, affordable electricity to their economies andcitizens. Increased electricity cooperation and tradebetween countries can enhance energy security, bringeconomies-of-scale in investments, facilitate financing,enable greater renewable energy penetration, and allowsynergistic sharing of complementary resources. Thisbriefing note draws from the experiences of RPSI schemesaround the world to present a set of findings to helpaddress these challenges. It is based on case studies of 12RPSI projects and how they are dealing with key aspects ofRPSI, such as: (i) finding the right level of integration;(ii) optimizing investment on a regional basis; (iii)appropriate regional institutions (iv) technical andregulatory harmonization; (v) power sector reform andintegration (vi) the role of donor agencies (vii) reducingemissions through RPSI; and (viii) RPSI and renewable energy.