Rosacea is a chronic facial dermatosis with a progressive course, which is characterized by the presence of erythema, papules, pustules, telangiectasias and sebaceous gland hyperplasia. However, the aetiology is still unknown; genetic predisposition, gastrointestinal disorders (Helicobacter pylori), infestations with Demodex folliculorum and environmental stimuli are considered to be involved in the inflammatory process. A metabolite of nicotinamide, 1-methylnicotinamide (MNA(+)), has anti-inflammatory properties, and this is the first study to test the effectiveness of this agent in treating rosacea. In total, 34 patients with rosacea were treated with a gel containing 0.25% MNA(+) as a chloride salt, twice daily for 4 weeks, after which improvement was observed in 26/34 cases. The improvement was good in 9/34 and moderate in 17/34, but no clinical effect was noted in seven subjects. In only one case was skin irritation given as the reason for treatment withdrawal. These results indicate that MNA(+) might be a useful agent for treating rosacea.