A contoured aeromagnetic map of the Muertos Trench, Puerto Rico–Virgin Islands Platform, Puerto Rico Trench, and outer ridge provides new information concerning the structure of this region. The lithology, age, and structure of magnetic rocks north of the Puerto Rico Trench may be similar to those of the pre-Oligocene rocks of Puerto Rico. There appears to be no major fault on the north side of the Puerto Rico Trench. A major fault (possibly a thrust fault) with a vertical separation of at least 2 km is buried beneath the middle Tertiary and younger sedimentary rocks of the north side of the Puerto Rico–Virgin Islands Platform. The magnetic patterns are consistent with an origin by block faulting for the Anegada Passage and the Virgin Islands Basin. There is a possible chain of submarine volcanoes south of and parallel to the Puerto Rico–Virgin Islands Platform.