Familial spastic paraplegia (FSP), characterized by progressive spasticity of the lower extremities, is in its "pure" form generally of autosomal dominant inheritance pattern. Hazan et al. [Nat Genet 5:163-167, 1993] reported tight linkage of a large FSP family to the highly polymorphic microsatellite marker D14S269 with z (theta) = 8.49 at theta = 0.00 They further demonstrated evidence for locus heterogeneity when they showed that 2 FSP families were unlinked to this region. We have subsequently studied 4 FSP families (3 American, one British) and excluded the disease locus in these families for approximately 30 cM on either side of D14S269, thereby confirming evidence for locus heterogeneity within the spastic paraplegia diagnostic classification.