Of the genus Vavaea, occurring from Sumatra to Fiji, 356 collections were studied for taxonomical purpose, some collected in spirit by the author himself. Pollen (31 collections) and wood (12 collections) were also studied. Sex dimorphism occurs in V. amicorum, three sorts of plants being distinguished. The systematic position within Meliaceae comes in the Melioideae, between tribes Turraeeae and Trichilieae, more closely related to the latter. Within Vavaea two sections are distinguished, one of which is new. Four species are distinguished, among which is one new species, V. tubiflora, from New Guinea. A detailed study revealed that one of them, the type species V. amicorum, is an extremely polymorphic species with about 20 synonyms; a special chapter is dedicated to explain this variation pattern. A key to the species, descriptions of genus and species, and an enumeration of specimens is given.