Purpose : We assessed the relationship between peak growth hormone level with growth velocity, insulin-like growth factor-1(IGF-1)/ IGF binding protein-3(IGFBP-3) ratio and sellar magnetic resonance image(MRI) of pediatric patients with idiopathic growth hormone deficiency. Methods : Among the patients presented with short stature between Jan. 2000 to Dec. 2012, patients with idiopathic growth hormone deficiency who had been regularly followed up in the pediatric endocrinology unit for more than 6 month were assigned to this study. They were treated with human growth hormone and we followed up these patients every 3 month with body measurements. And all the patients were evaluated for the bone age(BA) and serum values of IGF-1 and IGFBP-3. Subjects were divided into two groups based on whether their peak growth hormone level in growth hormone stimulation test for diagnosis of idiopathic growth hormone deficiency is under 5 ng/ml(Group I, N=9) or 5 ng/ml and above(Group II, N=21). We compared the anthropometric parameters, height standard deviation score(HT SDS), initial BA delay, growth velocity, IGF-1/IGFBP-3 ratio and sellar MRI finding between two groups. Results : The results of anthropometric parameters, HT SDS and initial BA were similar between two groups. There is no significant difference of growth velocity at 6 month(Group I vs Group II; 3.8 cm vs 3.7 cm, i＞P/i＞ =0.657), 1 year(Group I vs Group II; 8.6 cm vs 7.7 cm, i＞P/i＞ =0.304), 2 year(Group I vs Group II; 8.2 cm vs 7.0 cm, i＞P/i＞ =0.351), 3 year(Group I vs Group II; 7.3 cm vs 7.4 cm, i＞P/i＞ =0.931) after start of treatment between two groups. The ratio of IGF-1/IGFBP-3 showed no significant difference at 1st (Group I vs Group II; 0.11 vs 0.18, i＞P/i＞ =0.657), 2nd(Group I vs Group II; 0.12 vs 0.09, i＞P/i＞ =0.492), 3rd(Group I vs Group II; 0.13 vs 0.12, i＞P/i＞ =0.805) follow-up. There is no association of peak growth hormone level with neurogenic problem of sellar MRI (i＞P/i＞=1.0). Conclusion : Based on our findings, we consider that there is no correlation between peak growth hormone level as of 5 ng/ml and growth velocity as well as IGF-1/IGFBP3 ratio and neurogenic problem of sellar MRI.