Mosses (Bryophyta) comprise about 12 800 species in the world. In Mexico, 984 species and varieties are recognized from literature records and specimens in the Bryophyte Collection of the National Herbarium (MEXU). The southern states and those along the Neovolcanic Belt are the richest in terms of number of species, but the botanical exploration elsewhere may still produce many records. The proportion of endemic taxa is low in most vegetation types, except in the alpine areas where it reaches 17% while it is only 8% at the national level. Moss diversity is concentrated in 25 out of 75 families that contain 792 species and varieties (80% of the moss flora); the most diverse family is the Pottiaceae with 158 species and varieties. Ease of dispersal and longevity are considered responsible for the low level of moss endemism in Mexico. Only 6 species are officially recognized as rare or endangered, but many others are at risk because of forest and microhabitat disturbance by man.