Autosomal dominant familial spastic paraplegia (FSP) is a degenerative disorder of unknown aetiology characterized by a progressive spasticity of the legs. Three families with autosomal dominant FSP of early onset were analysed in linkage studies using highly polymorphic microsatellite markers. Close linkage to a group of markers on chromosome 14q (maximum multipoint lodscore z = 10) was observed in one family. This chromosome 14q candidate region was entirely excluded in the two other families, providing evidence of genetic heterogeneity within a homogeneous clinical form of FSP.