Objective. Red cell distribution width (RDW) which is reported as part of complete blood count in routine clinical practice, is a measure of variability in size of the erythrocytes in the circulation. It is a novel predictor of mortality both in unselected populations and in some selected group of patients. We aimed to search whether RDW values differ between the healthy population and the patients with pre-hypertension and hypertension who are otherwise healthy, considering the widely accepted role of RDW as a prognostic marker especially for mortality. Patients and methods. Patients who were diagnosed with prehypertension or hypertension for the first time according to the Joint National Committee (JNC) 7 criteria and otherwise healthy were enrolled to the study. One-hundred and twenty-eight patients with hypertension, 74 patients with prehypertension and 36 healthy controls participated in the study. Complete blood count, biochemistry and erythrocyte sedimentation rates were measured by standard methods. Hemoglobin, white blood cell count, mean corpuscular volume, platelet count and RDW were recorded. Results. After adjustment for age, hemoglobin level, presence of anemia, serum uric acid level, erythrocyte sedimentation rate and mean corpuscular volume, mean RDW values were 15.26 +/- 0.82, 16.54 +/- 0.91 and 13.87 +/- 0.94 in prehypertensive, hypertensive and control groups, respectively (p < 0.05). Systolic and diastolic blood pressures were strongly correlated with RDW (r = 0.848 and r = 0.748, respectively; p < 0.01). Conclusion. RDW is higher in prehypertensive and hypertensive patients compared with healthy controls independently of age, inflammatory status and anemia. Higher RDW values are strongly correlated with higher systolic and diastolic blood pressures.