Patients with GH insensitivity, typically resulting from mutations affecting the GH receptor (GHR), GHR signaling cascade, or the IGF-I gene, are, generally, unresponsive to GH therapy. Beginning in the 1990s, clinical trials of IGF-I administration in such patients demonstrated both short- and long-term efficacy, although not to the degree observed with GH treatment of naïve GH-deficient patients. Adverse effects, including hypoglycemia, lymphoid overgrowth, benign intracranial pressure, and coarsening of facial features, have been observed, but, in general, have proven to be transient. As interest in the potential efficacy of IGF-I treatment for children currently labeled as idiopathic short stature increases, it will be important to have controlled clinical trials of GH, versus IGF-I versus combination, GH + IGF-I.