Sugarcane bagasse was pretreated by wet oxidation (WO) at 195 degrees C for 15 min under either alkaline, neutral or acidic conditions, and by steam explosion (STEX) at 205 degrees C for 10 min. Alkaline WO was more favourable than neutral and acidic WO for the following enzymatic hydrolysis of cellulose, giving 792 g kg(-1) glucose yield after 48 h. The enzymatic hydrolysis of the fibres in the whole slurry was inhibited by inhibitory compounds contained in the prehydrolysate in comparison with the hydrolysis of the washed solid fibres in buffer. The inhibition increased proportionally with formic acid concentration in the pretreated liquid fraction. Cellulose conversion was higher for simultaneous saccharification and fermentation (SSF) than for separate hydrolysis. The highest SSF conversion (829 g kg(-1)) was obtained for the material treated by alkaline WO. The fermentability of the prehydrolysates by Saccharomyces cerevisiae was evaluated. Stronger inhibition of ethanolic fermentation was observed in the prehydrolysate obtained by steam explosion. The inhibition was more noticeable for the volumetric productivity than for the ethanol yield. The volumetric productivity was reduced by 94.5 and 91.2% for STEX and WO, respectively, whereas the ethanol yield was reduced only by 45.2 and 31.0%, correspondingly, for STEX and WO. Furan aldehydes seemed to be mainly responsible for the inhibition of the fermentation. (c) 2006 Society of Chemical Industry.