The anthropometric response to 7 years of GH treatment was assessed in 11 short children with Russell-Silver syndrome (RSS) and in 5 with non-dysmorphic intrauterine growth retardation (NRSS). GH treatment induced a significant increase (p < 0.0001) in the mean height standard deviation score (SDS) and at the 7-year follow-up a height appropriate for the natural history of final stature in NRSS/RSS was already attained. An appreciable growth rate was still present with final height being attained only in 2 girls. There was no significant change in height SDS for bone age. Multiple regression analysis showed only chronological age at the onset of GH treatment was a predictor of gain in height SDS during GH therapy. These findings suggest that early GH treatment improves long-term growth in children with NRSS/RSS. Moreover, final height attainment is required for a definitive assessment of the beneficial effect on adult stature. Bone age assessment is not a reliable parameter to predict final height outcome in these children.