Aim: It is estimated that treatment options which lower endothelin (ET) levels may be a new treatment approach for hypertensive patients. For this purpose in this study, we investigated whether the antihypertensive effect of valsartan is due to its effect on serum ET levels or not. In addition to this, the relationship between serum ET evels and left ventricular hypertrophy (LVH) was also determined. Material and Method: Twenty-three patients (14 men, 9 women) with an age range of 33-70 years having Stage 1 (n=3) or Stage II (n=20) hypertension according to the criteria defined by the Joint National Committee Report VII (JNC VII) were included. Results: Compatible to previous studies, serum ET evels of the hypertensive patients were higher than of the healthy controls (p<0.05). In the hypertensive group, there were significant reductions in both ET levels and LVH after three months of valsartan and/or hydrochlorothiazide treatment (p<0.05). Serum ET levels of patients with LVH or hypertensive retinopathy were higher than patients without LVH or hypertensive retinopathy, however this finding was not statistically significant (p>0.05). Discussion: Valsartan was found to be effective in decreasing serum ET levels in addition to its beneficial effect on hypertension. In addition to this, serum ET levels were observed to be elevated in hypertensive patients. However, valsartan did not seem to be effective in the development of complications related to hypertension.