Familial transmission of del (18p) syndrome from a mother to her daughter is rare and has been reported only once before. We report a female patient referred to us at age 18 years because of mental retardation associated with short stature. Similar clinical features are also seen in her mother. Chromosome analysis revealed a 46,XX, del (18) (p11.2) karyotype in both the proposita and her mother. Fluorescence in situ hybridization with whole chromosome paint for chromosome 18 showed no evidence of translocation. Because of the familial transmission of del (18p), this case has wider implications in genetic counseling.