Height, expressed as standard deviation scores for chronological age and for bone age, was studied in relation to glomerular filtration rate, bone age delay, and bone histology in 47 children with chronic renal disease and GFR <80 ml/min/1.73 m2. In multiple regression analysis in all 47 patients, only GFR and bone age delay significantly affected height; 40% of children were short (height standard deviation score <-2) for chronological age, and 9% were short for bone age. Renal osteodystrophy, which only occurred at GFR <30 ml/min/1.73 m2, significantly affected height only in children with congenital renal disease and GFR <20 ml/min/1.73 m2. Although radiological and biochemical changes of renal osteodystrophy were seen more often in short children, histological bone disease occurred just as frequently in tall children as in short children. Thus much of the observed height retardation in chronic renal failure is associated with delayed skeletal maturation. In addition, although severe renal osteodystrophy may contribute to growth retardation in advanced renal failure, our data suggest that milder degrees of bone disease evident only on histological study cannot be implicated in the etiology of growth failure in chronic renal impairment.