After the initial two weeks, all individuals will undergo a meal profile test, after a 12-hour overnight fast, which consists of measurement of daylong plasma glucose, free fatty acids, and insulin responses to standard meals. Food for the test will be prepared by GCRC Metabolic kitchen. In order to assess the degree of postprandial and day-long hyperinsulinemia and the benefits of rosiglitazone on the metabolic abnormalities in patients with poor glycemic control, we plan to measure plasma glucose, free fatty acids, and insulin concentrations before 8 am and at hourly intervals for four hours after breakfast at 8 am and four hours after lunch at noon in response to identical test meals containing (as percentage of calories) 15% protein, 40% fat, and 45% carbohydrate. Baseline blood samples for fasting lipid and lipoprotein concentrations will be obtained after an overnight fast on the day of the meal profile. Cholesterol and lipoprotein subclasses will be analyzed by VAP-II method which is based on continuous enzymatic analysis of cholesterol and lipoprotein classes separated by a single vertical spin centrifugation using a controlled-dispersion flow analyzer. Hemoglobin A1C will be measured by an affinity chromography assay at baseline and at the end of the study.