Artificial keys to the genera of blue-green, red, brown, and green marine benthic algae of Micronesia are given, including virtually all the genera reported from Palau, Guam, Commonwealth of the Northern Marianas, Federated States of Micronesia and the Marshall Islands. Twenty-two new species or genera are reported here for Guam and 7 for Yap; 11 of these are also new for Micronesia. Note is made of several recent published records for Guam and 2 species recently raised from varietal status. Finally, a list is given of nomenclatural changes that affect the 2003 revised checklist. An interactive version of the keys is included in the algal biodiversity website at http://university.uog.edu/botany/474.