The usefulness of the detection of 14-3-3 protein in the cerebrospinal fluid (CSF) in the diagnosis of Creutzfeldt-Jakob disease transmitted from human growth hormone was evaluated in 20 French patients. The 14-3-3 protein was rarely detectable within the first 3 months of the disease but always positive after 7 months associated with the aggravation of the disease and the occurrence of dementia. 14-3-3 detection was not predictive of the survival time of the patients. The genotype at PRNP codon 129 could influence the timing of appearance of the 14-3-3 protein in the CSF.