Subcutaneous insulin substitution is not physiological. Despite the many attempts using intensified insulin regimens to render current insulin substitution protocols more physiological, a nondiabetic circulating insulin profile cannot be simulated in patients with type 1 diabetes. Despite many efforts, the pharmacological treatment of type 1 diabetes consists of an unphysiological attempt to substitute only one of the hormones which are lost after beta-cell destruction, namely insulin. It is therefore mandatory to search for additional means to achieve physiological regulation of glucose homeostasis and overall metabolic status. Peptides which are being developed as additional new therapeutic compounds for type 1 diabetes include, for example, IGF-I, leptin, C-peptide and amylin. In addition, the application of insulin analogues has already been introduced into clinical practice. However, so far none of these pharmaceutical compounds has been shown to offer real clinical benefits and substantially improve metabolic control in patients with type 1 diabetes. The results of long-term clinical trials using the peptide compounds listed above for the treatment of type 1 diabetes are still not available.