 Laboratory Tests. Measurements of fasting plasma glucose Beckman Glucose Analyzer, HbA1c 32 insulin 33 and C-peptide 34 by radioimmunoassay, and free fatty acids by HPLC 35 will be performed in the principal investigators laboratory at the Texas Diabetes Institute, as previously described. Assays for VCAM and ICAM 3, p-Selectin and s-Selectin 4, PAI-1 and endothelin-1 36, and plasma lipids by MRS 37 and apolipoproteins 38 will be performed in the laboratories of the Diabetes Division at the University of Texas Health Science Center. Measurements of IRS-1 thyrosine phosphorylation, PI-3 kinase activity and association of PI-3 kinase with IRS-1 also will be performed in the Diabetes Division laboratory. 