K. Schumann's classification of Alpinia (Zingiberaceae), which subdivided the genus into five subgenera and 27 sections, was based, in the main, on the character of the secondary bracts (bracteoles). It is here proposed that the subgenera be reduced to two—Alpinia (7 sections and 10 subsections) and Dieramalpinia (4 sections and 2 subsections), and that the character of the labellum (petaloid or non-petaloid) be used as the main differentiating criterion. Such a classification shows the centre of distribution of subgen. Alpinia, in which the labellum is petaloid, to lie north of the equator; subgen. Dieramalpinia, in which the labellum is non-petaloid, or rarely so at the apex only, is now excluded from continental Asia and has its main concentration east of Wallace's line with its greatest number of species in New Guinea. Stigma types have been examined when possible and, so far, they substantiate the proposed classification.

Keys to the subgenera, sections and subsections, together with distribution maps are provided. In Appendix 1 all published names in Alpinia are listed and annotated. Appendix 2 gives a key to the terminally-flowered genera of subfamily Alpineae; this is followed by five new names and six new combinations in Alpinia while A.cordylinoides is transferred to Riedelia.

Twenty-two species of Alpinia hitherto placed in sections Psychanthus and Pleuranthodium are transferred to the genus Psychanthus Ridley. The justification for the acceptance of Psychanthus, which is based on the cup-shaped character of the labellum is discussed, and the necessary new combinations made.

The morphological difference between the monospecific genus Brachychilum and Hedychium is bridged by the recently described Hedychium muluense R. M. Smith. Cytological studies reported here show that at least one stock of B. horsfieldii (Wall.) O. Petersen shares the same basic chromosome number and morphology with Hedychium. The genus Brachychilum should therefore be placed in synonymy with Hedychium, and B. horsfieldii should revert to Hedychium horsfieldii [R. Brown ex] Wall.