Insulin-like growth factor-I (IGF-I) is a naturally occurring single chain polypeptide of 7649 Da that is produced primarily in the liver. The metabolic activities of IGF-I are similar to those of insulin and its effects on growth, development, regeneration and metabolism have been widely studied. Indeed, IGF-I is currently being used clinically for the treatment of growth related disorders and its therapeutic value is also being evaluated in diabetes, IGF-I-induced neuroprotection, and in promoting bone healing. However, like many other peptides, IGF-I has a short biological half-life and is rapidly removed from circulation following systemic administration. In the vascular system, this is normally compensated for by the association of IGF-I with IGF-binding proteins (IGFBPs), that also appear to regulate the activities of IGF-I. Here, we describe the biopharmaceutical properties of different parenteral formulations of IGF-I. The pharmaceutical characteristics of conventional formulations such as aqueous IGF-I solutions are compare with new controlled release formulations such as multivesicular liposomes, osmotic minipumps, and poly (DL-lactic-co-glycolic) acid (PLGA) microspheres.