The pathophysiological mechanism of hypertensive retinopathy (HR) is not fully established. Elevated blood pressure alone does not fully account for the extent of retinopathy so other pathogenic mechanisms may be involved, such as increased platelet activation. Mean platelet volume (MPV) is a marker of platelet activation. Therefore, this study was designed to answer the following questions: Do MPV levels change in HR? and is there any relation between degree of HR and MPV levels? This study included newly diagnosed and 57 untreated essential hypertensive patients with HR. The hypertensive patients were divided into two groups according to the Keith, Wagener classification. Group 1 comprised 29 hypertensive patients with grade 1 HR with a mean age of 56.8 +/- 9.7 years. Group 2 comprised 28 hypertensive patients with grade 2 HR with a mean age of 58.1 +/- 10.3 years. Twenty-seven normotensive subjects who were the healthy participants and had undergone the check-up program were used as the control group. Fundoscopic examination, metabolic parameters and MPV levels were measured in all groups. The level of MPV in group 2 was significantly higher than in group 1 (8.9 +/-0 0.8 fl vs. 8.3 +/- 0.8 fl, p = 0.02) and the normotensive control group (8.9 +/- 0.8 fl vs 7.8 +/- 0.7 fl, p < 0.001). It was also higher in group 1 than in normotensive control group (8.3 +/- 0.8 fl vs.7.8 +/- 0.7 fl, p < 0.01). In addition, MPV showed a positive correlation with the degree of HR in the hypertensive group (r = 0.41, p = 0.015). Our study suggests that platelet activation, a mechanism known to be involved in vascular lesions, may promote the development of HR.