Black Sigatoka (aka black leaf streak), caused by the fungus Mycosphaerella fijiensis, and Moko disease, caused by the bacterium Ralstonia solancearum phylotype II, are among the most destructive diseases of banana. Black Sigatoka first appeared in the Western Hemisphere in Honduras in 1972, and then spread rapidly to other producing areas on the mainland. However, its movement in the Caribbean Islands has been slower and less extensive. The history of Moko disease is similar, in that it is widely spread in mainland tropical America but is still absent on most of the Caribbean Islands. Inter-island dispersal of M. fijiensis and R. solancearum is constrained by several factors. The pathogens are disseminated most effectively by man, but are thought to spread naturally up to, respectively, 200 and 90 km. Given the later possibilities and the distances that are involved, natural spread in most outbreaks of these diseases in the Caribbean cannot be ruled out. Only the arrival of black Sigatoka in Cuba, Florida and Jamaica, and that of Moko disease in Grenada and Jamaica are clearly the result of anthropogenic dissemination. The future spread and impact of these diseases in the region is discussed.