"This treatment is a taxonomic study of the benthic species of Ochrophyta known from Puerto Rico, Caribbean Sea. In all, 3 classes, 10 orders, 16 families, 33 genera and 77 species occur in the benthic marine communities in Puerto Rico. Of these, 3 species of Sargassum are found only as unattached and free-floating. A brief summary of phycological studies in Puerto Rico and ecological descriptions of the most common marine habitats are presented. Along with date, place and author(s) of valid publication for all genera and species, type locality information and descriptive accounts of vegetative morphological and reproductive anatomy are provided. Distribution of each species is given, and where relevant, comments on their habitat, and taxonomic and nomenclature are discussed. A key to the genera and keys to species within genera are included. Either an in situ or other illustration accompanies most species. Two new geographical distribution records for Puerto Rico and a description of one new species, Lobophora brooksii D. L. Ballant. et J. N. Norris are included"--