Rewilding falls within the general framework of restoration ecology, but differs from a traditional view of habitat restoration and species reintroduction. Four initial steps are required to instigate a rewilding project: identification of the issue of conservation concern; identification of the missing ecological processes; identification of the functional characteristics required; and selection and reintroduction of the most suitable species. One method of progressing rewilding to a mainstream management option is to test a priori hypotheses with quantifiable outcomes within rewilding projects. Scenario planning and the 'three horizons' analysis allow long-term rewilding projects to be considered in three phases: the current, functionally deficient ecosystem in need of restoration; a projected future scenario where the ecosystem is restored to a functional and self-sustaining state; a transition state between the first and third horizons. This chapter explores the proposed restoration of the Caledonian pine forest in the Scottish Highlands as an example. © 2013 John Wiley & Sons, Ltd..