High-pressure reactive extraction of Eucalyptus globulus wood was undertaken. Extractions were carried out with CO2 + 1,4-dioxane mixtures at 170 bar pressure at temperatures of 160-180 degrees C. The influence of temperature, extraction time, composition of the fluid mixture, and flow rate on the extraction were investigated. In the range of temperatures studied, only a small increase in lignin and hemicellulose extraction is observed when temperature is increased. At 180 degrees C, the degradative extraction of cellulose starts, but at lower temperatures, cellulose losses are small. The selectivity of the extraction depends upon the composition of the extracting mixture. CO2-rich fluid mixtures extract hemicellulose preferentially and total hemicellulose removal can be achieved. Maximum delignification was obtained by extraction with pure dioxane with 75% of the lignin initially present in wood being removed. Selectivity towards lignin vs. hemicellulose extraction increases with increasing flow rate until a plateau is reached.