A comprehensive study of structure and floristics in a typical montane (2700 m) grassland/forest transition in Papua-New Guinea was made using a destructive technique involving complete removal of all woody species below 10 m, in a single belt transect. By this means the distribution of all tracheophytes in a dense transitional system was accurately determined, providing evidence that the transition was advancing over open grassland. Use is made of profile and plan drawings. The transition is described as a discrete community in terms of juvenile, mature, and senescent phases. A distinct group of transition species is recognized. The distributions of life-forms and a symbiotic relationship between moss-hummocks and transition species are discussed, and the role of fire in transition dynamics is briefly considered.