A summary of the geology of northern French Guiana includes brief discussions of the stratigraphy, tectonics, dolerite dikes, Quaternary deposits and mineral resources. Precambrian rocks, which constitute a major part of the area, are represented by a discordant series ranging between 4000 and 1800 m.y. in age, which have been metamorphosed by successive granitization and intrusions of basic rocks. Two tectonic depressions, oriented in an ESE-WNW direction, occupy part of the area, one in the north extending halfway into Surinam, the other in the central region. Dolerite dikes up to 70 km long strike NNW-SSE. Transgressions and regressions in the Quaternary resulted in the deposition of three series of sediments on fossiliferous Eocene beds. Gold deposits, the basic resource of the country, seem to be related to the Caribbean granitization. A table correlates the stratigraphy of French Guiana, Guyana, and Surinam.