Linear growth retardation and adult short stature are usual characteristics of Prader-Willi syndrome. Several lines of evidence suggest that a deficiency in growth hormone (GH) secretion may contribute to this abnormal growth pattern. We have recently reported observations in 4 children with Prader-Willi syndrome treated with GH. This report extends our observations in 2 of these cases. Both cases had abnormally low growth rate, normal stimulated GH levels, and low somatomedin-C levels prior to therapy. GH treatment led to significant increases in linear growth rate and somatomedin-C levels. An additive effect of oxandrolone therapy on linear growth rate was demonstrated in one case. Our results support the possibility of a neuro-secretory GH deficiency in Prader-Willi syndrome and suggest a need for further investigations.