Maryland is a middle Atlantic seaboard state. It is the ninth smallest state in the Union (10,460 sqare miles). The State is geologically complex and contains parts of five physiographic provinces: Coastal Plain; Piedmont; Blue Ridge; Ridge and Valley; Appalachian Plateau. The last checklist of Maryland mosses was compiled in 1949. The present checklist-with 47 families, 126 genera, 334 taxa-is based on the examination of more than 5,000 collections as well as a survey of the literature on Maryland mosses. The checklist is arranged alphabetically by family; distribution of the taxa is documented at the county level. Baltimore County has the most, while Somerset County has the least recorded taxa. This checklist includes 98 taza reported for the first time from Maryland.