Advances in genetic engineering will make possible treatment of many pediatric endocrine disorders with replacement therapy. Some of these conditions include short stature, precocious puberty, and diabetes mellitus. Although the availability of such hormonal replacement offers new treatment modalities, an understanding of their mechanism of action and pharmacologic characteristics is crucial to maximize their effectiveness while minimizing possible untoward effects. The clinician must evaluate potential risks and benefits as these substances come to market without definitive answers being available as to their long-term effects.