The edematogenic properties of insulin have long been documented, although they have been underestimated despite current trends toward intensive insulin therapy. Insulin treatment has been associated with weight gain, mild or moderate edema, and, rarely, generalized edema and cardiopulmonary congestion. In addition, the use in recent years of thiazolidinediones, which improve insulin sensitivity, has been associated with weight gain and peripheral edema, which can progress to pulmonary edema, particularly when thiazolidinediones are used in combination with insulin. This article attempts to raise awareness about the overlooked edematogenic action of insulin. In addition, the potential role of edema-provoking properties of insulin in the development of vascular complications in patients with diabetes is discussed.