Diabetes mellitus (DM) is characterized by renal hemodynamic changes which have been purported to contribute to the development of nephropathy. In this review we have focused on the major renal hemodynamic factors that may be associated with glomerular hyperfiltration. Recent animal and human studies have demonstrated that renal hemodynamic alterations occur very early in the natural history of DM. Most of the literature related to renal hemodynamic functional changes in type 1 DM has focused on major neurohormonal influences, such as the renin angiotensin system, cyclooxygenase-related pathways, the nitric oxide system, the autonomic nervous system and hyperglycemia. In addition, gender may have important modulatory effects on some of these putative pathways that have been implicated in the development of alterations in renal hemodynamic function related to DM.