Purpose: Demodex folliculorum (DF), which is frequently found in patients with chronic blepharitis, is a well-known common inhabitant of eyelash follicles. In the present study, the prevalence of DF in seborrheic blepharitis patients and controls was investigated. In addition, the associations between the presence of DF and host factors (age, sex) were analyzed. Methods: A prospective, cross-sectional study was done involving 500 cases. In all, 6000 cilia from 170 patients with seborrheic blepharitis and 330 patients with normal eyes were examined for DF. Twelve eyelash samples were epilated from each patient and examined under the light microscope. Results: DF was found in 28.8% (49/170) of patients with blepharitis and in 26.7% (88/330) of controls. The difference between the two groups was not statistically significant. The overall prevalence was 27.4% (137/500) in all patients. Although the prevalence of DF increased with increasing age, no significant difference was found between the age groups. There was also no statistically significant difference for DF prevalence between males (28.9%; 71/246) and females (24.1%; 61/254). Conclusion: Our findings show a high DF prevalence in both blepharitis and control patients and no relationship was found between the presence of DF and host factors (age, sex).