The present study was started as a revision of the Gesneriaceae of Suriname (Dutch Guiana). As it proved to be impossible to solve the taxonomic problems on the base of the scanty material from that country only and as the region of the three Guianas inclusive of the Brazilian territory “Amapá” and the Venezuelan “Delta Amacuro” turned out to be a sufficiently natural floristic unit, the author decided to extend his investigations to all Gesneriaceae known from that area. Of those species material of many herbaria was studied in order to obtain a more complete impression of individual variation and geographical distribution. Among the material borrowed for this purpose the author came across misidentified (and unnamed) specimens some of which belonged to undescribed species. When the material was sufficiently ample and well-preserved new descriptions were drawn up; in some cases new combinations (transfers to other genera) were necessary. For the genera Chrysothemis and Napeanthus complete revisions were made, because otherwise it would have been impossible to work out properly the taxonomy of the Guiana species.