This work is the first comprehensive listing of the mosses that occur in tropical America since Mitten's Musci Austro-Americani published in 1869. Over 4,000 species and infraspecies are catalogued. The distribution for each name is given on a country-by-country basis for the area (Mexico south to the northern borders of Argentina, Chile, Paraguay, and Uruguay) plus the West Indies, and for general regions outside the area.