Several glycosidase activities were measured in frontal gray matter of 4 brains from subjects affected by Creutzfeldt-Jakob disease. The changes of N-acetyl-beta-glucosaminidase, N-acetyl-beta-galactosaminidase, beta-glucosidase, alpha-fucosidase and alpha-mannosidase were not statistically significant but significant increases of beta-glucuronidase and beta-galactosidase activities were found. These results are in accordance with several reports on brain glycosidases in scrapie and Semliki Forest virus-infected brain and could explain some changes in brain glycoconjugate content previously observed in human and experimental Creutzfeldt-Jakob disease.