In adults many studies have shown abnormalities of endothelial cell function. In the control subjects t-PA levels rose significantly post occlusion. This rise was significantly reduced in the diabetic subjects especially those with microvascular complications. PAI levels fell post occlusion in all normal subjects and there was a smaller but still significant fall in the diabetics without complications. In the complicated group however levels were increased or unchanged post occlusion in all but two subjects though this did not reach statistical significance.