This work was undertaken at the suggestion of Dr. J. Lanjouw and Dr. F. P. Jonker. The citation heading this paragraph indicates that the group of Caryophyllaceae with which it deals, presents unusual taxonomic difficulties. At first, it was intended to restrict the revision to the genus Gypsophila. However, in the course of the work it was realized that the small genera Bolanthus, Ankyropetalum and Phryna could not be left out of account as they had been regarded by some authors as subdivisions of Gypsophila and by others as near relatives of this genus. For this reason a complete revision of these genera too was included. The only previous revision of Gypsophila is that published by Williams (1889). His study, largely based on data derived from the literature, includes 76 species i.e. about 3/5th of the number recognized here. His views on the generic limits were strongly influenced by those expressed by BENTHAM in BENTHAM and HOOKER’s Genera Plantarum 1 (1862). Later authors did not follow him in this respect, and generally preferred BOISSIER’s delimitation (1867), so e.g. PAX and HOFFMANN in the 2nd Edition of ENGLER und PRANTL, Planzenfam. (1934). PAX had already accepted this delimitation in the first edition (1889).