Phosphatase and beta-glucosidase, which are hydrolases bound to humic substances, were determined in the extracts of humic substances and in their fractions (F) of varying molecular weight (F-1 < 10(3) low, F-2 < 10(3)-10(4) intermediate and F-3 > 10(4) high) obtained from cow and sheep manure and their corresponding vermicomposted products (casting). In both of these products F-2 was the fraction with the highest C and N content, while the F-1 fraction lost the greatest proportion of C during vermicomposting. Phosphatase and beta-glucosidase could be detected in all the fractions studied, whether these were from the extracts of the manure or from the casting. However the enzymatic activity found in the extracts was less than the total activity of all the fractions summed, which demonstrated that an increase in activity was obtained as a consequence of the ultrafiltration. IEF spectra pointed to bands of humic substances with higher isoelectric points (I-p) in the castings than in the corresponding manures. Most of the beta-glucosidase in cow manure (as determined in humic bands appearing in the polyacrylamide gel after IEF) corresponded to humic bands which focused at I-p between 4.1 and 4.7, while in cow manure casting most of the activity was in bands with I-p between 5.1 and 6. In sheep manure and casting the bands which showed beta-glucosidase activity also showed phosphatase activity. Both in the extract and in its different fractions beta-glucosidase and phosphatase activity increased with IEF. IEF spectra showed that humic substances of the casting had higher enzymatic activity than those of the corresponding manures.