Background: Microalbuminuria (MAU) has been reported as a predictor of atherosclerotic cardiovascular disease (CVD) in patients with diabetes (DM) or hypertension (HBP). The aim of this study was to evaluate the association between MAU and other predictors of atherosclerosis. We also determined which of 2 aspects of atherosclerosis, arterial thickness or stiffness, more highly correlates with MAU in each DM and HBP. Methods: Total 113 patients (mean age: 55.9짹5.5years) initially diagnosed as type 2 DM or essential HBP without overt nephropathy were enrolled. Urinary albumin-to-creatinine ratio (ACR) was assessed before initial treatment to define MAU as ACR���22 (men), ACR���31mg/g (women). Arterial stiffness was assessed by aortic pulse-wave velocity (PWV) and arterial thickness was measured by carotid intima-media thickeness (IMT). Several predictors of CVD, such as hsCRP, left atrial volume index (LAVI), ankle-brachial index (ABI) were also assessed. Results: MAU was observed in 53 patients (29 of HBP, 24 of DM) and 60 patients (41 of HBP, 19 of DM) had normoalbuminuria (NAU, ACR<22 in men, ACR<31mg/g in women). In comparison between MAU and NAU groups, there was no difference in age, gender, body mass index, and duration of disease. However, levels of hsCRP, IMT, PWV were significantly higher in MAU than in NAU group (2.9짹1.4 vs 0.8짹0.4mg/L, 1.08짹0.17 vs 0.66짹0.12mm, 19.5짹2.9 vs 14.5짹1.5m/sec, p<0.05, respectively). In subgroup analysis, DM with MAU had significantly higher level of hsCRP, IMT, PWV than DM with NAU group (3.1짹0.8 vs 0.9짹0.4mg/L, 1.11짹0.16 vs 0.69짹0.09mm, 19.9짹3.1 vs 15.5짹1.5m/sec, p<0.05, respectively). In HBP, the results were similar (2.7짹1.8 vs 0.7짹0.4mg/L, 1.05짹0.17 vs 0.64짹0.13mm, 18.2짹2.2 vs 14.1짹1.2m/sec, p<0.05, respectively). In comparison between DM with MAU and HBP with MAU groups, ACR was higher in DM with MAU than in HBP with MAU (95.6짹49.2 vs 66.7짹35.2mg/g, p<0.05). The levels of hsCRP and IMT were not statistically different in both groups, however, level of PWV was significantly higher in DM with MAU than in HBP with MAU group (19.9짹3.1 vs 18.2짹2.2m/sec, p<0.05). There was no difference of LAVI and ABI in all comparisons. Conclusions: In both early DM and early HBP, MAU was strongly associated with increased arterial thickness (IMT), stiffness (PWV), and hsCRP. Interestingly, DM with MAU demonstrated more increased level of PWV, but not IMT, than HBP with MAU group. This result suggests that correlation between MAU and arterial stiffness could be more obvious in early DM than in early HBP.