Three methods of soil nitrogen availability assessment have been compared in Mediterranean forest soils: successive hydrolysis, autoclaving and short-term aerobic incubation. The results of autoclaving were similar to those obtained in the first hydrolysate (1N HCI for 3 hours) and correlated well with the N mineralised in the aerobic incubation. The aminoacid fraction was the major component in the hydrolysates; the first hydrolysate accounted for most of the hydrolysable organic N. The autoclave method is postulated to be the most useful as an index of soil N availability in the soils studied.