ICRP Publication 77 reaffirms the Commission's current policy of radiological protection, in particular its policy on public exposure, and aims to clarify the practical application of that policy to the disposal of radioactive waste. It discusses the justification of a practice, the optimisation of protection, the use of collective dose assessed over long distances and times, the implications of potential exposure, and the distinction between practices and intervention. In particular, it explains why collective doses should not be ignored simply because the individual doses contributing to it are small. However, it also stresses that collective doses may need to be presented separated into blocks of limited ranges of dose and time, and forecasts of collective dose over long time should include a critical examination of their uncertainty. This report is expected to be important to anyone dealing with radiation protection policy, obviously in the context of waste disposal, but also in general because of the explanations of the Commission's policy concerning collective dose.