Following a 2003 report on the threat of invasive alien species in the Caribbean, CAB International (CABI), together with a range of national, regional and international partners, developed a proposal titled 'Mitigating the Threats of Invasive Alien Species in the Insular Caribbean'. The Global Environment Facility (GEF), through the United Nations Environment Programme (UNEP), recently accepted the proposal for a Project Development Facility Block A (PDF-Α) Grant. This will enable consultations at the national and regional / international levels, aimed at developing a full-size project (FSP) covering invasive aliens species strategies, prevention, control etc. for marine, freshwater and terrestrial systems with wide stakeholder participation. However, before this, further consultation and project planning will take place during a Project Development Facility Block Β (PDF B) phase. This paper describes various elements of the proposal and outlines steps involved in the process of the development of the FSP.