Two siblings with familial lissencephaly presented with the clinical and neuropathological features of the Miller-Dieker syndrome. High resolution caryotype demonstrated a 46,XX,-17+der(17)t(15;17)pat translocation with partial deletion of the short arm of chromosome 17 in one patient and a balanced 46,XY,t(15;17)(q2600;p1300) translocation in the father. Review of the literature uncovered 14 additional patients with Miller-Dieker syndrome and partial deletion of the short arm of chromosome 17. A cytogenetic study should be done in all cases of lissencephaly for genetic counselling.