Hereditary hemihypotrophy hemiparesis hemiathetosis syndrome (HHHH; OMIM 306960) was first reported in a family with congenital left hemiplegia in two males and moderately affected females. We describe a family with three males demonstrating congenital right hemiplegia with porencephalic lesions of the left internal capsule and putamen, or the periventricular white matter just above the internal capsule. Clinical findings within each family are limited to the same side, though sidedness differed between families. Both pedigrees were most consistent with X-linked inheritance. Genome-wide linkage analysis in our family further supports a locus for HHHH on chromosome X.