South Africa has the world's richest temperate flora, with 20,456 indigenous vascular plant taxa recorded. With the current estimate of the global flora at 379,881 taxa, 5% of the world's plant diversity is represented within South African borders. Between 2004 and 2008, South African botanists completed a comprehensive assessment of the status of the South African flora using the International Union for Conservation of Nature and Natural Resources (IUCN) Red List categories and criteria, version 3.1. South Africa is the first floristically megadiverse country to fully assess the status of its entire flora and to achieve Target 2 of the Global Strategy for Plant Conservation (GSPC): “[a]n assessment of the conservation status of all known plant species, as far as possible, to guide conservation action.” Herein, we discuss the critical success factors that allowed an assessment of such a megadiverse flora within five years. Establishing a centralized team of ecologists to develop Red Lists, collaborating with a wide range of botanical experts, streamlining the assessment process via automation, and establishing a data management system that served local conservation needs were crucial to the success of the project. Utilizing the IUCN categories and criteria proved to be, and is suggested as, the most cost-effective measure for other megadiverse countries wanting to achieve Target 2. Quantitative assessments can be done with minimal data, and comprehensive assessments of all known taxa ensure conservation attention for a greater proportion of a flora. The example of South Africa demonstrates that conservation assessments can be done relatively cheaply in developing megadiverse countries (less than $30 per taxon for South Africa). As megadiverse countries have high numbers of endemic plant taxa, it is well worth the investment by IUCN and conservation donors to support continued and future assessment projects.