A three-year floristic analysis of the mosses of Dysart Woods, an old-growth forest in Belmont County, Ohio, led to the collection of 39 taxa distributed among 17 families and 28 genera. Species and frequency of occurrence varied considerably between slope aspect (north vs. south) and among substrate types. Six and 13 species were collected exclusively from the north- and south-facing slopes, respectively, and 20 species were common to both slope aspects. Woody debris was the most floristically diverse substrate on north-facing slopes (65% of species) while woody debris and exposed soil on a hiking trail were equally important habitats on south-facing slopes (39 and 33% of species, respectively). Twenty of the species collected at Dysart Woods represent new reports for Belmont County. The collections from this study bring the number of families, genera, and species of Belmont County to 29, 57, and 82, respectively.