We hypothesize that the majority of the information needed to accurately estimate insulin sensitivity is contained in the fasting insulin and glucose levels as well as the insulin and glucose levels obtained shortly after an intravenous glucose load. We propose to test this hypothesis by performing both hyperinsulinemic euglycemic glucose clamps as well as intravenous glucose tolerance tests on normal volunteers and groups of patients with diabetes, hypertension, or obesity (diseases known to be associated with insulin resistance). Data from these studies will be used obtain estimates of insulin sensitivity by the glucose clamp method, minimal model method, and a novel analysis that utilizes only fasting and peak levels of glucose and insulin. We hope to devise a simpler method for determining insulin sensitivity in vivo that is suitable for testing large populations. This method will require only a few blood samples, take less than one hour to perform, and correlate with glucose clamp estimates at least as well as the minimal model method.