beta-Xylosidase (EC 3.2. 1.37) belongs to an enzyme complex, the xylanases, which cleave xylans and release xylosyl residues by endwise attack of xylo-oligosaccharides. Precipitation was performed with ethanol at concentrations of 20, 40, 60 and 80% at different pH values (4.6, 5.9, 6.3 and 7.0), in order to compare the behaviour of beta-xylosidase with the behaviour of total xylanase present in the medium. In addition, a fractional precipitation of these enzymes was performed in three steps under the most suitable of all the conditions tested (pH 4.6, 4 degrees C and 20, 60 and 80% ethanol concentrations). In the first step (20% ethanol), around 10% of beta-xylosidase and 80% of total protein precipitated, and in the second step (60% ethanol), 75% of the same enzyme precipitated. The remaining xylanolitic complex (82%) precipitated in the third step (80% ethanol). The electrophoresis analysis showed that the enzymes can be selectively separated by ethanol precipitation according to their molecular weights. The kinetic parameters (K-M and V-M) of beta-xylosidase before and after the precipitations remained constant. The separation process did not affect the kinetic characteristics of the enzyme.