AbstractTransects across the margins of rainforests with eucalypt forests at two sites in New South Wales are described. At Girard State Forest along ten transects it was consistently found that pure rainforest occurs where there is no evidence of past burning; and that rainforest tree species appear to be invading and replacing eucalypt forest through a formerly burned ecotone area. A similar pattern was found at Barrington Tops. It is suggested that adaptations shown by species of tall open forests which enable them to regenerate rapidly after burning may have evolved initially in a fire free, prehuman rainforest environment in response to other types of disturbance.