OBJECTIVES: Hereditary spastic paraplegia (HSP) is a heterogeneous group of neurodegenerative disorders characterized by a progressive gait disorder, lower limb spasticity, hyper-reflexia, weakness and extensor plantar responses. Recently, large intronic hexanucleotide repeat expansions (GGGGCC) in C9ORF72 have been found to cause frontotemporal dementia (FTD), amyotrophic lateral sclerosis and FTD with motor neuron disease. Owing to the overlapping phenotypes among HSP, amyotrophic lateral sclerosis and FTD with motor neuron disease along with shared pathological findings, we hypothesized that C9ORF72 expansions might be a genetic risk factor or modifier of HSP. METHODS: Clinically characterized HSP patients were investigated for elongations in the hexanucleotide repeat of C9ORF72. RESULTS: Upon analyses of the repeat lengths in the C9ORF72 gene in a Danish cohort of HSP patients, we found no expansions. CONCLUSION: We conclude that HSP is most likely not associated with repeat expansions in C9ORF72.