We report three sisters showing the clinical features and investigational findings of Cockayne syndrome (CS). In the rehabilitation unit of Northwest Armed Forces Hospital (N.W.A.F.H.), Tabuk, Saudi Arabia, there was a 12-year-old girl with typical features of CS. The girl had no apparent problems until the end of the first year when growth and developmental delay prompted medical evaluation. Brain CT, bone X-rays, auditory and ophthalmological evaluation confirmed the clinical impression of Cockayne syndrome. Two of her 13 sibs, both sisters, were later found to have the same syndrome. The sisters varied in clinical severity, as two of them had cataracts and early global delay and died early of inanition and infection. The third showed the disease manifestations at a relatively later age, did not have cataract, exhibited milder manifestations of the disease, and remains alive. The parents are not related by any way and the father is married to two other wives with 11 unaffected children. This report documents variable degrees of manifestations in sibs who presumably have the same gene mutation. © 2000 Wiley-Liss, Inc.