Homocysteine has been demonstrated to play a causal role in atherosclerosis and to predict cardiovascular events in the general population. On the other hand, left ventricular (LV) hypertrophy and diastolic dysfunction assessed by echocardiography can also predict cardiovascular events in patients with cardiovascular risk factors. However, there are few data regarding the relationships among homocysteine, LV hypertrophy, and diastolic function. We examined the relationships among homocysteine, LV mass index, and diastolic function in 1082 patients (63±14 years, Male gender: 63%), who had diabetes. Echocardiography was performed to measure the left ventricular mass index (LVMI) as a parameter of LV hypertrophy. LV diastolic function was assessed by the ratio (E/A) of early (E) and late (A) diastolic transmitral flows, early diastolic mitral annular velocity (Em), and the ratio (E/Em) of E to Em using Doppler echocardiography. E/Em ratio was categorized as E/Em<8, 8≤E/Em<15 and E/Em≥15. The homocysteine was correlated with E/E`` (r=0.328, p<0.001) and LVMI (r=0.187, p=0.031). Homocysteine was increasing with increasing E/Em grade (11.7±5.2 vs 12.8±7.0 vs 13.5±6.9;E/Em<8 vs 8≤E/Em<15 vs E/Em≥15 respectively, p=0.04) (figure). The E/Em as a parameter of LV diastolic function showed the close correlation to homocysteine. These results indicate that elevated homocysteine reflects LV diastolic dysfunction. Therefore, we suggest that homocystein may be a marker of LV diastolic dysfunction in patients with diabetes.