The marine benthic brown algae of the north coast of Papua New Guinea (mainly from Madang province) are documented, based on collections made by the first author, between 1980 and 1990. All records [34 identified taxa (+Sargassum spp.)] are listed with bibliographic, taxonomic, nomenclatural and biogeographical notes. The specimens belonging to the genus Dictyota are identified according to recent species definitions. D. magneana De Clerck et Coppejans is described as new to science. Only some representatives of the genus Sargassum have been identified to species level. The phaeophycean flora of the north coast is very similar to that of the south coast (Port Moresby area); nevertheless some differences can be observed. © 2001 Adac/Éditions scientifiques et médicales Elsevier SAS.