Fire is recognised as a potent ecological factor in woody and bushy environments. In this investigation the effect of experimental fire on soluble organic C and N, soil microbial biomass C and N, the bacteria/fungi ratio and soil enzymatic activities were measured 12 and 18 months after fire in a Lithic Xerocrept soil. The soil soluble C was changed both by fire and sampling time in burned soils, whereas soluble N did not show any clear trend. The enzymatic activities were decreased by fire, but a peak of activity was recorded in soil burned at 309 °C, which corresponded with the highest recorded soluble C. A quantitative reduction in soil microbial biomass C and N was observed. © INRA, EDP Sciences, 2004.