Fuel characteristics of four forest types (Eucalyptus forest, Callitris forest, Mixed Eucalyptus/monsoon thicket, Pure monsoon thicket) with distinct fire regimes, were compared. The Eucalyptus forest had the highest frequency of fires (2-3 years interval). It had a sparse litter layer with a low moisture content but the greatest biomass of grass fuels. These grasses had rapid rates of flame spread, variable sustainabilities and low energy contents. Callitris forest has a small grass component and the lowest mass of fuel of the four sampled communities. The Callitris forest litter was more moist than the Eucalyptus forest, possibly because of its greater canopy cover. Of the infrequently burnt communities the mixed Eucalyptus/Monsoon thicket had more evidence of previous fires than the adjacent Pure monsoon thicket. Both communities has similar loads of energy rich, flammable litter, but differed in the positively related measures of little moisture content and canopy cover. Moisture content of the litter before the wet season was one half that after the summer rains. With the exception of the grasses there was no corresponding decrease in the flammability of individual fuel components. The interrelated measures of litter moisture, fuel density and abundance of grass appear to best explain the differences in the fire regimes of the four communities studied. The lack of corresponce between community fire-regime and measures of fuel flammability suggest that there has been no natural selection for fire-promoting characteristics in northern Australian vegetation, perhaps reflecting the extremely high frequency of natural and anthropogenic fires. Circularity of the hypothesis that vegetation evolves characteristics to promote fire makes validation or rejection extremely difficult.