This document sets out a practical, science-based approach to spatial biodiversity assessment and prioritisation, which can be applied at the national level in any country. It is especially useful for countries that are both biodiversity rich and resource constrained, where difficult choices have to be made about how and where to focus conservation action. This document shows how even the most data-poor country can use available global data as the basis for an initial spatial assessment and prioritisation that will yield useful results. The core intended audience is those individuals involved in revising or implementing NBSAPs, although the approach has many other wider applications.