Introduction: In this study, we aimed to investigate the factors that determine response to growth hormone (GH) treatment in children with isolated idiopathic GH deficiency treated in our university hospital. Materials and Methods: The data of 149 patients followed in our university hospital between January 1995 and December 2005 were evaluated in patient charts retrospectively. Results: The maximum GH response to clonidine and glucagon stimulation tests was 4.58 and 6.01 ng/ml respectively. The mean GH dose was 0.215 (0.18-0.25) mg/kg/week. Height SDS significantly increased after the first and second years of GH treatment (p<0.05). There was a negative correlation between the maximum response to stimulation tests and the response to GH treatment (p<0.05). When the patients were grouped according to the maximum response to stimuli as <3, 3-5, 5-7, and >7 ng/ml, the best response to therapy was observed in the group with the least response (<3ng/ml) to both clonidine and glucagon stimulation tests. A positive correlation was determined between height gain and GH dose, and a negative correlation between height gain and age at the beginning of therapy (p<0.05). There was no correlation between target height, baseline pubertal stage, relative weight and IGF-1 SDS with the response to GH treatment (p>0.05). Conclusions: Patients who were started treatment at an early age, whose response to GH stimulation tests were lower, and who were given higher doses benefited more from GH treatment. Therefore, we suggest that the diagnostic criteria for GH deficiency must be reevaluated and the random cut-off of <10 ng/ml for stimulated GH level may lead to overdiagnosis. This issue must be further investigated in larger patient populations with consideration of final height as well. © The Journal of Current Pediatrics, published by Galenos Publishing.