Background: Adequate muscle perfusion is required for the maintenance of skeletal muscle mass. Impairments in microvascular structure and/or function with aging and type 2 diabetes have been associated with the progressive loss of skeletal muscle mass. Objective: To compare muscle fiber type specific capillary density and endothelial function between healthy young, older men and age-matched type 2 diabetes patients. Design: 15 healthy young men (24+/-1 y), 15 healthy older men (70+/-2 y), and 15 age-matched type 2 diabetes patients (70+/-1 y) were selected to participate in the present study. Whole-body insulin sensitivity, muscle fiber type specific capillary density, sublingual microvascular density and dimension of the erythrocyte perfused boundary region were assessed to evaluate the impact of aging and/or type 2 diabetes on microvascular structure and function. Results: Whole body insulin sensitivity was significantly lower at a more advanced age, with lowest values reported in the type 2 diabetic patients. In line, skeletal muscle capillary contacts were much lower in the older and older type 2 diabetic patients when compared with the young. Sidestream darkfield imaging showed a significantly greater thickness of the erythrocyte perfused boundary region in the type 2 diabetic patients compared with the young. Conclusions: Skeletal muscle capillary density is reduced with aging and type 2 diabetes and accompanied by impairments in endothelial glycocalyx function, which is indicative of compromised vascular function.