The frequency of a recently described point mutation of the ciliary neurotrophic factor (CNTF) gene was investigated in a population of 154 German patients with motor neuron disease (MND). Twenty-two percent of the patients were heterozygous, 2% homozygous for the CNTF mutation. Since the gene defect is per se not linked to MND, the identification of additional gene defects occurring simultaneously with this mutation could be informative for the understanding of pathogenic mechanisms of MND.