Accurate estimates of forest cover and forest fragmentation are critical for developing countries such as Costa Rica, which holds four to five percent of the world's plant and bird species. We estimated forest cover for Costa Rica using Landsat 5 Thematic Mapper satellite scenes acquired between 1986 and 1991. In 1991, 29 percent (ca 14,000 km²) of the land cover of Costa Rica was closed forest cover; of that forested area, ca 30 percent is protected by national conservation policies. Forest loss in a study area representing ca 50 percent of Costa Rica's territory during a five-year period (1986–1991) was 2250 km², and the estimated deforestation rate was ca 450 km²/yr, or ca 4.2 percent/yr, of remaining forest cover. Forests are almost completely eliminated from the Tropical Moist Forest and Premontane Moist Forest life zones, and the level of fragmentation of remaining forests may be more advanced than previously thought.