Establishment of appropriate basal insulin levels is an essential component of intensive insulin therapy. While the existence of a "dawn phenomenon" is widely recognized, the present study sought to establish whether diurnal basal insulin patterns exist in Type-1 diabetes, and whether these patterns vary by age and gender. Participant data was drawn from 322 Type-1 insulin pump users treated at a private diabetes education practice in suburban Philadelphia. All participants completed a battery of fasting tests designed to match basal insulin levels to endogenous glucose production and insulin sensitivity. Analysis of resultant basal patterns revealed significant differences between juvenile (age < or =20) and adult (age >20) basal insulin patterns. The younger group exhibited a more pronounced and sustained night-time peak; the older group exhibiting a briefer and less pronounced early-morning peak. Lower overall basal insulin requirements were found in the youngest (age < or =10) and oldest (age >60) groups. No noteworthy gender differences were found. Results can serve as a guide for clinicians when initiating and fine-tuning patients who utilize basal/bolus insulin therapy.