There have been few quantitative studies of edge effects in tropical rainforest fragments. I used physiognomic edaphic and floristic data from 52 900-m2 plots to describe edge effects in such fragments in NE Queensland Australia. Relative to unfragmented forest forest fragments ranging from 1[middle dot]4 to 590 ha in area had higher canopy and subcanopy damage and exceptional abundance of heavy lianas climbing rattans Calamus spp. and other disturbance-adapted plants (Dendrocnide spp. Solanum spp.). Elevated forest disturbance was evident up to 500 m inside fragment margins although the most striking changes occurred within 200 m of edges. Application of these data with a mathematical ‘Core-Area Model’ suggested that isolated nature reserves in NE Queensland must exceed 2000-4000 ha depending on reserve shape to ensure that >50% of the reserve remains unaffected by induced forest.