Rosacea is a common chronic inflammatory facial skin disease predominantly affecting the central part of the face. Despite numerous scientific studies by Russian and foreign scientists, the etiology and pathogenesis of rosacea have not been fully understood. Rosacea affects up to 15% of the adult population, and its prevalence among all dermatoses is up to 5%. In recent years, the particular importance in the pathogenesis and clinical course of rosacea has been attributed to the worm-like mite Demodex folliculorum. There is ample evidence to show that most rosacea patients have a high number of Demodex folliculorum mites in skin lesions, and therapy with topical medication leads to their eradication. This is often associated with an improvement or solution of rosacea symptoms. This article presents the current data on the role of Demodex folliculorum in the clinical course of rosacea and describes the disease course in 82 rosacea patients. Demodex folliculorum was found in 55 of the patients. The disease was more severe, clinical, subjective symptoms were more pronounced, and signs of ocular rosacea were more frequent in patients with Demodex folliculorum versus those in whom it was not detected.