The hardbottom, patch, and bank reefs of Biscayne National Park (BNP) are among the most northern reef communities in the Florida Keys reef tract. The close proximity of BNP reefs to highly developed areas (i.e., the greater Miami metropolitan area) make them both heavily used and susceptible to a multitude of anthropogenic stresses. This study analyzes a unique 1977–1981 data set on stony-coral abundances and percent cover, collected from eight reefs in BNP, and compares this more than 25-year old data set with published data from surveys conducted from 1994–1996 and 1998–2000. In 1977–81, stony-coral cover on the eight reefs ranged between 8% and 28%, whereas coral cover reported from surveys in 1998–2000 ranged between 0.4% and 10%. Significant declines in cover of all coral species were seen at BNP reefs in the ? 20 years between data sets, although few changes were observed in species richness and taxonomic distinctness values. Spatial differences were observed between lagoonal patch reefs and outer bank reefs, consistent with previous reports of greater loss of coral cover on offshore reefs. Previous reports have suggested that high juvenile coral mortality due to fish predation, physical stresses, and thermal stresses have contributed to reduced cover at offshore BNP reefs.