Rapid population ageing has led to repeated adjustments to the parameters of Japan's public pension scheme over the last decade, all aimed at achieving long run financial balance. The most recent attempt, describe in this paper, introduces an adjustment mechanism that links future benefit levels to the underlying determinants of the scheme's finances. This mechanism is similar to those recently introduced in Germany and, to a lesser extent, in Sweden, and fundamentally alters the concept of the 'defined benefit'. Changes to how pension reserves are invested are also described. Finally, the benefit reductions in the public scheme and recent regulatory changes suggest an increased future role for complementary private provision.