The Japanese pension system is today confronted with diverse problems notably linked to the ageing of the population and the diversification of lifestyles and work methods. Old age threatens the continuity of pay-as-you-go pension schemes. The result is that the Japanese pension schemes are losing the confidence of their beneficiaries, some of whom refuse to contribute, which poses a number of fundamental legal questions on the justification of compulsory contribution. The evolution of lifestyles, notably women’s employment, emphasises the pension schemes’unequal treatment of employed and unemployed women, which is due to the fact that the mechanics of this scheme do not take individual lifestyle choices into account. Additionally, this problem poses questions about the nature and range of solidarity and redistribution in pension schemes. The objective of the 2004 Japanese pension system reform was to adapt the system to social changes.