The present paper uses a comparison of Japan and the US to argue that the debate about corporate governance reform is best framed in terms of systems of complementary instruments and institutions. It argues that the Japanese and US systems of corporate governance differ along many dimensions, yet can both be understood as efficient combinations of complementary instruments adapted to a particular institutional and regulatory environment. The paper also shows how exogenous shocks and piecemeal regulatory reforms have undermined the internal consistency of the Japanese system in the recent past.