For those individuals who have diabetes, a letter or direct verbal permission will be obtained, prior to coming to this study visit, from your eye doctor indicating that you can take part in one of the tests listed below. During this visit, an electrocardiogram (EKG, usual heart rhythm test performed in a doctor's office) will be performed. Your heart rate will also be measured for six minutes with an EKG machine while breathing as deeply as possible. This test, which will be performed twice, will tell whether or not the nerves that go to the heart are normal. You will be asked to blow into a plastic tube for 15 seconds (this is the test for which we will obtain the eye doctor's permission for individuals with diabetes). Your heart rate will be measured during and for 60 seconds after you have finished blowing. This test, which will be performed twice, will tell if the nerves that go to blood vessels are normal. Your blood pressure will be measured four times, one minute apart, while you are lying down. You will then be asked to stand up and your blood pressure will again be measured four more times, each time one minute apart. Change in your heart rate will also be determined as you go from lying down to standing. All individuals will have a fingerstick blood sugar level performed prior to the performance of the tests describe above.